Usmle-mcq's-8

<1>A 61-year-old woman with leukemia abruptly develops an intensely
itchy rash. Physical examination demonstrates multiple erythematous
patches of the distal arms and legs, some of which involve the palms
and soles. Some of the patches show central clearing with surrounding
erythematous rings. Which of the following is the most likely diagnosis?
A. Erythema migrans chronicum
B. Erythema multiforme
C. Kaposi's sarcoma
D. Psoriasis
E. Urticaria
Answer
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<2>A 52-year-old woman presents to her physician for a check-up. She is
recovering from a wrist fracture after a fall. Dual energy x-ray
absorptiometry of the hip had shown her to have osteoporosis. She
became menopausal at age 50 and did not begin hormone replacement
therapy because of a strong family history of breast cancer. She
now fears a future hip fracture and would like to begin a bone
loss prevention regime.Which of the following pharmaceutical
agents is most appropriate for this patient?
A. Calcitonin nasal spray
B. Oral conjugated estrogen
C. Raloxifene
D. Tamoxifen
E. Transdermal estradiol

Answer
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<3>A fracture of the humerus neck damages a nerve running around the humera
l neck. After the fracture heals, the patient notices a marked decrease in
his ability to raise his arm over his head. The denervated muscle arises
from which of the following?
A. Acromion alone
B. Clavicle and acromion
C. Clavicle and coracoid
D. Coracoid alone
E. Coracoid and acromion
Answer
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<4>A patient is admitted to a psychiatric hospital after having been picked
up by the police for making inappropriate sexual advances. A detailed
psychiatric interview demonstrates deficits in memory, insight,
judgement, personal appearance, and social behavior. The patient
is witnessed experiencing a possible epileptic seizure. Over a
period of several years, motor findings also develop, including
relaxed, but expressionless facies, tremor, dysarthria, and pupillary
abnormalities. Which of the following tests performed on his
cerebrospinal fluid would most likely be diagnostic?
A. CSF glucose
B. FTA-ABS
C. Gram's stain
D. Lymphocyte count
E. Neutrophil count
Answer
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5.A 42-year-old man has just been informed that he has poorly
differentiated small cell carcinoma of the lung. When asked if he
understands the serious nature of his illness, the patient proceeds
to tell his physician how excited he is about renovating his home.
This patient is exhibiting
A. denial
B. displacement
C. projection
D. rationalization
E. reaction formation
F. sublimation
Answer
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<6>A 3-month-old infant presents with a 3-day history of fever, cough,
and poor feeding. On examination, the baby appears ill and has a
temperature of 102 F and a respiratory rate of 32. A chest x-ray
film shows bilateral patchy infiltrates in the lungs. Which of
the following is the most likely etiologic agent?
A. Coronavirus
B. Influenza type A
C. Parainfluenza type 1
D. Respiratory syncytial virus
E. Rhinovirus
Answer
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<7>A 35-year-old male presents to the urologist for an infertility
evaluation. A biopsy of his testis is performed to check sperm production
and maturation. A microscopic section reveals only a few germ cells near
the basal lamina in the seminiferous tubule. Which of the following cells
is the germ cell closest to the basal lamina in the seminiferous tubule?
A. Primary spermatocyte
B. Secondary spermatocyte
C. Spermatid
D. Spermatogonia
E. Spermatozoa
Answer
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<8>A 30-year-old otherwise healthy woman presents to her physician with
complaints of fatigue and dyspnea. Physical examination reveals normal
breath sounds and the presence of third and fourth heart sounds. Chest
x-ray shows clear lung fields but right ventricular enlargement, main
pulmonary artery enlargement, and "pruning" of the peripheral vasculature.
Electrocardiogram shows right axis deviation and right ventricular
hypertrophy. Left ventricular function appears normal on echocardiography
. Serologic studies show antinuclear antibodies. Which of the following
pathological findings would this patient also show, either at autopsy
or if an appropriate biopsy was taken?
A. Mural thrombus of the right atrium
B. Necrosis and scarring of the left ventricle
C. Plexogenic pulmonary vasculopathy
D. Pulmonary artery stenosis
E. Severe pulmonary fibrosis
Answer
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<9>During an abdominal surgical procedure, the surgeon wishes to locate the
ureter in order to ensure that it is not injured. The ureter may be found
immediately anterior to the origin of the
A. common iliac artery
B. external iliac artery
C. internal iliac artery
D. gonadal artery
E. renal artery
Answer
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<10>A patient with mild congestive heart failure is treated with high-dose
furosemide and diureses 25 pounds of fluid. A complete blood count (CBC)
taken before the diuresis shows an RBC count of 4 million/mm3; a
CBC taken after diuresis shows a RBC count of 7 million/mm3.
Which of the following is the most likely explanation?
A. Cyanotic heart disease
B. Increased erythropoietin
C. Polycythemia vera
D. Relative polycythemia
E. Renal cell carcinoma
Answer
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<11>A newborn male child is noted to have hypospadias. A complete
evaluation determines that the child has no other genitourinary
anomalies. Nonetheless, hypospadias repair will be performed to
prevent which of the following possible sequelae?
A. Bladder exstrophy
B. Hydrocele
C. Phimosis
D. Urachal cysts
E. Urinary tract infection
Answer
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<12>During the passage of an intravenous catheter, numerous endothelial
cells are dislodged from the lining of the popliteal vein. What substance
allows platelet adhesion to the exposed collagen fibers?
A. Factor VIII
B. Factor IX
C. Fibronectin
D. Tissue factor
E. Von Willebrand factor
Answer
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<13>A 57-year-old man presents to the emergency department with a nosebleed
for the past 2 hours. The patient received a prosthetic heart valve 5
months ago and is currently taking warfarin (7.5 mg per day) and oral
antibiotics. Laboratory evaluation reveals an INR (international
normalized ratio, the ratio of patient to normal prothrombin times)
of 6.4. Which of the following antibiotics is the patient most likely
taking?
A. Ampicillin
B. Cephalexin
C. Nitrofurantoin
D. Norfloxacin
E. Phenazopyridine
Answer
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<14>A 47-year-old woman presents with complaints of nervousness and
increased sensitivity to hot weather. She is diagnosed with hyperthyroidism
and prescribed propylthiouracil. What is the principal mechanism by which
this drug acts?
A. Decreasing the efficacy of TSH binding to the thyroid TSH receptor
B. Decreasing the rate of proteolysis of thyroglobulin
C. Increasing the amount of 3,3',5'-triiodothyronine (reverse T3; rT3)
D. Inhibiting deiodination of thyroxine (T4)
E. Inhibiting the uptake of iodide into the thyroid gland
Answer
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<15>Which of the following neurotransmitters is most important for the
induction of REM sleep?
A. Acetylcholine
B. Dopamine
C. Epinephrine
D. Norepinephrine
E. Serotonin
Answer
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<16>A 37-year-old woman presents with 3 days of progressive joint pain in
her ankles, knees, and wrists. She had three similar episodes over the
past several years. On examination, she has a temperature of 38.7 C, her
blood pressure is 110/70 mm Hg, and her heart rate is 90/min. She has a
diffuse petechial rash over her trunk and extensor surfaces. Her ankles
and knees are swollen, red, and tender with decreased range of motion,
and there is tenderness over the tendon sheaths of her hands and
forearms. Blood cultures are negative. Aspiration of joint fluid
reveals a white cell count of 22,000/mm3 with no visible organisms,
but culture on chocolate agar is positive. Which of the following
is an attribute of the causative organism that allows it to produce
recurrent infections?
A. It is an intracellular pathogen
B. It is resistant to ceftriaxone
C. It is resistant to complement-mediated lysis
D. Its capsule is not immunogenic
E. Its pili undergo antigenic and phase variation
Answer
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<17>The data presented below compares the results of a diagnostic test in
the presence and absence of a disease.
Disease present Disease absent
Positive test 40 5
Negative test 10 95
Total 50 100
The specificity of the test is
A. 0.05
B. 0.40
C. 0.80
D. 0.90
E. 0.95
Answer
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<18>Blood stored in a blood bank tends, with time, to become relatively
depleted of 2,3-diphosphoglycerate. What effect does this have on the
hemoglobin-oxygen dissociation curve?
A. Shifts the curve to the left, so that the hemoglobin has a decreased oxygen affinity
B. Shifts the curve to the left, so that the hemoglobin has an increased oxygen affinity
C. Shifts the curve to the right, so that the hemoglobin has a decreased oxygen affinity
D. Shifts the curve to the right, so that the hemoglobin has
an increased oxygen affinity
E. Does not change the dissociation curve
Answer
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<19>A psychotic, indigent man with a history of multisubstance abuse has
been involuntarily hospitalized for 1 week. Because of persistent diarrhea,
stools are sent for ova and parasites, revealing numerous granular,
spherical, thin-walled cysts measuring 10-20 mm in diameter. Trichrome
stains show up to four nuclei in most of the cysts. These finding are
consistent with an infection by which of the following organisms?
A. Cryptosporidium parvum
B. Dientamoeba fragilis
C. Entamoeba histolytica
D. Giardia lamblia
E. Isospora belli
Answer
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<20>A child who understands that the volume of a liquid poured out of a
narrow glass remains the same when poured into a wider glass is at which
of Piaget's stages of intellectual development?
A. Concrete operations
B. Formal operations
C. Preoperational
D. Sensorimotor
Answer
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<21>A 4-year-old girl is brought to a specialty clinic by her foster parents
because of a limp in her right leg and a serum alkaline phosphatase (ALP)
that is 10 times the adult upper limit of normal for the test. The child
is withdrawn and clinging to her foster mother. Physical examination is
remarkable for a blue-green discoloration of the skin overlying a
tender, 3-cm mass on the anterior portion of the right mid-thigh.
An x-ray of the right thigh reveals a dense mass within the femur
that extends into the surrounding tissue. Which of the followin
best describes the increased alkaline phosphatase and physical
findings in this case?
A. ALP is abnormal for her age and the bone lesion represents an area of aseptic necrosis
B. ALP is abnormal for her age and the bone lesion represents repair of a femoral fracture
C. ALP is abnormal for her age and is unrelated to the bone lesion
D. ALP is normal for her age and the bone lesion is an osteogenic sarcoma
E. ALP is normal for her age and is unrelated to the bone lesion
Answer
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<22>Which of the following drugs antagonizes both the vascular and cardiac
actions of norepinephrine?
A. Atenolol
B. Esmolol
C. Labetalol
D. Metaproterenol
E. Prazosin
Answer
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<23>During surgery to treat an ischioanal abscess, the inferior rectal nerve
is damaged. This nerve is a direct branch of which of the following nerves?
A. Inferior gluteal nerve
B. Pelvic splanchnic nerve
C. Pudendal nerve
D. Sciatic nerve
E. Superior gluteal nerve
Answer
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<24>A 15-year-old girl is evaluated for failure to begin menstruation.
Physical examination demonstrates short stature and a webbed neck.
Chromosomal analysis demonstrates a lack of one X chromosome. This
patient should be specifically evaluated for which of the following
cardiovascular anomalies?
A. Coarctation of the aorta
B. Dextrocardia
C. Ostium primum septal defect
D. Pulmonary stenosis
E. Tetralogy of Fallot
Answer
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<25>A baby is born with a testicular mass. Histologic sections made of the
homogeneous yellow-white mass after its removal demonstrate
epithelial-lined spaces that have flattened-to-cuboidal epithelial
cells with vacuolated cytoplasm containing eosinophilic, hyaline-like
globules. Scattered structures resembling primitive glomeruli (endodermal
sinuses) are also seen. If appropriate immunohistochemical stains are
performed, the eosinophilic cytoplasmic globules would most likely
contain which of the following?
A. Alpha-fetoprotein
B. Estrogen receptors
C. Human chorionic gonadotropin
D. Human papilloma virus
E. Melanin
Answer
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<26>A surgeon wishes to perform a splenectomy on a patient who has been in
an automobile accident. Before removing the spleen, the splenic artery and
splenic vein are ligated. Within which of the following peritoneal
structures are the splenic artery and vein found?
A. Gastrocolic ligament
B. Gastrosplenic ligament
C. Lesser omentum
D. Splenorenal ligament
Answer
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<27>A 65-year-old woman with a long-standing disease has bone marrow
fibrosis and increased bone remodeling, with bone resorption exceeding
bone formation. She has a history of passing calcium-oxalate kidney
stones. Which of the following lab result profiles would be expected in
the serum of this patient?
Calcium Phosphate PTH
A. decreased decreased increased
B. decreased increased decreased
C. decreased increased increased
D. increased decreased increased
E. increased increased increased
Answer
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<28>Upon examination of a newborn male, a cystic structure is found in the
scrotum. It is determined that there is a hydrocele of the spermatic
cord. Which of the following is the most likely etiology of this finding?
A. Communication between the epididymis and the tunica
vaginalis
B. Failure of the processus vaginalis to form
C. Failure of the processus vaginalis to fuse
D. Incomplete fusion of the processus vaginalis
E. Varicosities of the spermatic vein
Answer
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<29>A Brazilian immigrant is hired at a meat-packing plant, and undergoes
an employment physical. Chest x-ray demonstrates a patchy, bilateral
pneumonia and a lung mass, and he is referred to a specialist. Biopsy
of the mass demonstrates fungal organisms with a few very
distinctive "pilot's wheel" yeast forms. Which of the following
is the most likely diagnosis?
A. Blastomycosis
B. Coccidioidomycosis
C. Histoplasmosis
D. Paracoccidioidomycosis
E. Sporotrichosis
Answer
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<30>A 34-year-old female is brought to the emergency room with severe
muscle cramps and carpopedal spasms. The patient was noted to be
extremely irritable and was complaining of tingling around the
mouth and in the hands and feet. A few hours later, laboratory
examination reveals sodium 140 mEq/L, potassium 4.2 mEq/L,
chloride 101 mEq/L, calcium 6.4 mg/dL, phosphate 5.1 mg/dL,
magnesium 2.4 (normal 1.8-3.8 mg/dL) and alkaline phosphatase
67 U/L. A CT scan of the head shows basal ganglia calcifications.
Prolonged QT intervals and T wave abnormalities are noted on
electrocardiogram. The history is pertinent for a thyroidectomy
two months prior to admission. Which of the following conclusions
is most consistent with these data?
A. An increase in dietary vitamin D is warranted
B. Hepatocytes have a low 25-hydroxylase activity
C. Intestinal cells are underexpressing calcium transporter genes
D. Isolated cells from the kidney have high 1-hydroxylase activity
E. The levels of 1,25-dihydroxy vitamin D are normal
Answer
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<31>A 48-year-old man presents to his physician with complaints of
dizziness and fatigue. Physical examination reveals a blood pressure
of 130/50 mm Hg and a heart rate of 100 beats per minute. On examination,
the physician notes a large scar on the patient's abdomen. The man states
that he was severely injured in an automobile accident several years ago,
and required abdominal surgery at that time. Which of the following is
the most likely diagnosis?
A. Arteriovenous fistula
B. Cardiac tamponade
C. Heart failure
D. Hypovolemia
E. Shock
Answer
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<32>A renal pathologist examining the day's kidney biopsies notes that one
biopsy shows amorphous red nodules within the glomerular mesangium in
hematoxylin and eosin stained material. Congo red stain of the biopsy
demonstrates apple-green birefringence of these nodules. These nodules
are most likely to be related to which of the following?
A. Acute urinary tract infection
B. Diabetes mellitus
C. Sarcoidosis
D. Systemic lupus erythematosus
E. Tuberculosis
Answer
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<33>A patient goes to his family doctor complaining of persistent and severe
headaches. His physician diagnoses migraine headaches and prescribes
sumatriptan. What is the mechanism of action of this drug?
A. Dopamine1 agonist
B. GABAB antagonist
C. Muscarinic3 antagonist
D. Non-selective beta antagonist
E. Serotonin1D agonist
Answer
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<34>A 60-year-old man presents to his physician after a routine screening
test indicates hyperlipidemia. Physical examination reveals raised,
irregular, yellow papules in the skin of the soft tissues below the
eyes. Biopsy of these lesions would most likely show which of the
following?
A. Benign nevus cells
B. Malignant nevus cells
C. Microscopic blisters
D. Munro microabscesses
E. Multinucleated giant cells
Answer
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<35> Trisomy 21 Normal karyotype
Positive test 100 50
Negative test 100 250
An experimental diagnostic test is developed to noninvasively detect the
presence of trisomy 21, Down's syndrome. The test is administered to a
group of 500 women considered to be at risk for a Down's fetus based
on blood tests. The results of this test are shown above. What is
the sensitivity of this new test?
A. 40%
B. 50%
C. 67%
D. 71%
E. 83%
Answer
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<36>An autopsy is performed on a 60-year-old man who developed progressive
dementia, parkinsonism, and visual hallucinations beginning 5 years prior
to death. Histopathologic examination reveals numerous eosinophilic
intracytoplasmic inclusions within neurons of substantia nigra,
limbic cortex, and basal nucleus of Meynert. These inclusions are
immunoreactive for ubiquitin. Which of the following is the most
likely postmortem diagnosis?
A. Alzheimer disease
B. Amyotrophic lateral sclerosis (ALS)
C. Diffuse Lewy body disease (dementia with Lewy bodies)
D. Parkinson disease
E. Pick disease
Answer
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<37>A 60-year-old factory worker reports to his physician that he can no
longer push heavy boxes across the floor. Upon examination it is noted
that the patient elevates the right shoulder when attempting shoulder
flexion, but shoulder abduction is not impaired. The medial border of
the right scapula is very prominent. Which of the following nerves
innervates the affected muscle?
A. Long thoracic nerve
B. Lower subscapular nerve
C. Musculocutaneous nerve
D. Suprascapular nerve
E. Upper subscapular nerve
Answer
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<38>The American Diabetes Association (ADA) recently lowered the cutoff
value for fasting glucose used in diagnosing diabetes mellitus from 140
mg/dL to 126 mg/dL. This reference interval change would be expected to
produce which of the following alterations?
A. Decrease the test's sensitivity
B. Increase the test's false negative rate
C. Increase the test's negative predictive value
D. Increase the test's positive predictive value
E. Increase the test's specificity
Answer
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<39>An emergency room physician examines a patient who has fallen from a
motorcycle and injured his shoulder. The clinician notices a loss of the
normal contour of the shoulder and a abnormal-appearing depression below
the acromion. Which of the following injuries did the patient most likely
sustain?
A. Avulsion of the coronoid process
B. Dislocated shoulder joint
C. Fracture of the mid shaft of the humerus
D. Fracture of the surgical neck of the humerus
E. Laceration of the axillary branch of the posterior cord
Answer
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<40>A 7-month-old child with failure to thrive is found to have a hemoglobin
of 4.4 g/dL. The peripheral smear shows very small red cells with marked
pallor. It is determined that the child has very low levels of hemoglobin
A, with elevated fractions of hemoglobin A2 and hemoglobin F. Which of
the following underlying mechanisms is most likely related to the
observed findings?
A. Amino acid substitution on b globin
B. Antibody against fetal blood cells
C. Cytoskeletal protein defect
D. Insufficient production of b globin
E. Iron deficiency
Answer
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<41>During a routine pelvic examination, a 20-year-old woman is found to
have an enlarged uterus. Ultrasound studies demonstrate a multiloculated
cystic structure within the uterine cavity, but no baby is identified.
This mass is removed with dilation and curettage of the uterus, and
placental-like tissue is observed during pathologic examination.
Which of the following tumor markers would be most useful in
establishing that residual tumor does not remain in the uterus?
A. b-hCG
B. Bombesin
C. CEA
D. PSA
E. S-100
Answer
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<42>On physical examination of a 7-year-old boy, the child's upper body
appears much more developed than his lower body. Blood pressure in the
upper extremities exceeds that of the lower extremities. On cardiac
examination, there is a midsystolic murmur over the anterior chest
and back. The child's lower extremities are cold, and femoral pulses
are absent. The part of the vascular system that is affected in this
disorder is derived from which of the following embryologic structures?
A. Bulbus cordis
B. Ductus arteriosus
C. Left horn of sinus venosus
D. Right common cardinal vein
E. Right horn of sinus venosus
F. Third, fourth, and sixth aortic arches
Answer
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<43>A 42-year-old obese woman experiences episodic abdominal pain. She notes
that the pain increases after the ingestion of a fatty meal. The action of
which of the following hormones is responsible for the postprandial
intensification of her symptoms?
A. Cholecystokinin
B. Gastrin
C. Pepsin
D. Secretin
E. Somatostatin
Answer
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<44>A 42-year-old man was in an automobile accident and suffered severe
pelvic trauma. The bulb of the penis and the urethra were torn from the
inferior surface of the urogenital diaphragm. This has allowed urine to
extravasate from the urethra. Into which of the following regions will
the urine flow?
A. Deep perineal space
B. Ischioanal space
C. Rectovesical pouch
D. Retroperitoneal space
E. Superficial perineal space
Answer
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<45>Karyotypic analysis of a spontaneously aborted fetus demonstrates
trisomy of one of the chromosomes. Which chromosome is most likely to
be affected?
A. 8
B. 13
C. 16
D. 18
E. 21
Answer
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<46>At which of the following locations might a penetrating wound to the
heart damage the AV node?
A. Apex of the heart
B. Interatrial septum
C. Interventricular septum
D. Wall of the right atrium
E. Wall of the left atrium
Answer
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<47>A 9-month-old infant is brought to the Health Department to receive the
second dose of OPV (oral polio vaccine) 2 weeks after the first vaccination.
The child has mild diarrhea, so the decision is made to defer further
immunizations. Bacteriologic examination of a stool culture is
unremarkable; however, a small, single-stranded, positive RNA
virus is isolated from the specimen. This same agent was
isolated from sewage effluent the preceding week. The
viral isolate was not inactivated by ether. Which of
the following viruses was most likely isolated?
A. Adenovirus
B. Hepatitis C
C. Parvovirus B19
D. Poliovirus
E. Rotavirus
Answer
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<48> Section of synovium from the knee joint of a patient with rheumatoid arthritis (RA) is taken. Which of the following are
the most abundant cells in the inflammatory infiltrate?
A. Eosinophils
B. Langhans type giant cells
C. Lymphocytes and plasma cells
D. Neutrophils
E. Type A and B synovial cells
Answer
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<49>A 54-year-old African-American female patient undergoes a routine
insurance physical examination. Chest x-ray reveals bilateral hilar
masses. Biopsy of the masses shows granulomata, but acid-fast and
fungal stains are negative for organisms. Which of the following
diseases should be suspected?
A. Caroli's disease
B. Raynaud's disease
C. Sarcoidosis
D. Scleroderma
E. Systemic lupus erythematosus
Answer
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<50>A neuroscientist discovers a way to selectively label neural crest
cells in a developing laboratory animal. After birth, he sacrifices the
animal and examines the tissue to search for labeled cells. Which of
the following cell types will contain the label?
A. Astrocytes
B. Ependymal cells
C. Microglia
D. Oligodendroglia
E. Pseudounipolar cells
Answer
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Answers
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1>B 11>E 21>*** 31>A 41>A
2>*** 12>*** 22>C 32>*** 42>*** 23> 33> 43> C
3>*** 13>D 23>*** 33>E 43>A
4>*** 14>E 24>A 34>*** 44>***
5>A 15>*** 25>*** 35>B 45>C
6>D 16>C 26>B 36>C 46>B
7>D 17>E 27>*** 37>A 47>D
8>C 18>B 28>*** 38>C 48>C
9>B 19>C 29>D 39>B 49>C
10>D 20>A 30>*** 40>D 50>E

usmle-mcq's-7

(42) <1>An 18-year-old college student presents to the student health
center complaining of a sore throat and fever. He describes feeling
tired for the past few days and reports a loss of appetite. On
examination, he has pharyngitis with cervical lymphadenopathy.
Blood tests reveal lymphocytosis and the presence of heterophil
antibodies. Which of the following best describes the virus
responsible for his illness?
A. Double-stranded, enveloped DNA virus
B. Double-stranded, nonenveloped DNA virus
C. Single-stranded, enveloped RNA virus
D. Single-stranded, nonenveloped DNA virus
E. Single-stranded, nonenveloped RNA virus

Answer
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<2>Which of the following organisms is a natural transformer?
A. Escherichia coli
B. Neisseria gonorrhoeae
C. Plasmodium vivax
D. Pseudomonas aeruginosa
E. Staphylococcus aureus
Answer
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<3>A child psychiatrist would like to evaluate the intellectual
ability of a 3-year-old patient. Which of the following is the
most appropriate test for him to use?
A. Denver Developmental Scale
B. Stanford-Binet Scale
C. WAIS-R
D. WISC III
E. WPPSI
Answer
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<4>A 57-year-old woman with a 30-year x 2 pack/day history of cigarette
smoking undergoes bronchoscopy. Biopsy of bronchial tissue show
s replacement of the normal pseudostratified ciliated columnar
epithelium with stratified squamous epithelium. This change
represents
A. dysplasia
B. hyperplasia
C. malignant transformation
D. metaplasia
E. necrosis and repair
Answer
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<5>A 25-year-old woman presents to her physician with complaints of
easy bruising and excessive bleeding. Physical examination demonstrates
hepatosplenomegaly. A blood smear reveals pancytopenia and a bone marrow
biopsy demonstrates markedly enlarged cells containing a fine fibrillar
material resembling tissue paper. Leukocyte enzymatic studies demonstrate
a deficiency of beta-D-glucosidase activity. Which of the following
substances is most likely to accumulate in the bone marrow cells?
A. Galactose
B. Glucosylceramide
C. Glycogen
D. Homocysteine
E. Mineralocorticoids
Answer
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<6>A 34-year-old HIV-positive man without previous opportunistic
infections presents complaining of dyspnea with daily activity. He
states that he has had a mild cough and fever but denies having had
chills, sputum production, or chest discomfort. Physical examination
is remarkable for oral thrush and a few small, nontender cervical
lymph nodes. A chest x-ray film reveals bilateral interstitial
infiltrates, and bronchoalveolar lavage reveals small silver-staining
cysts. In which other patient population in the U.S. is this organism
a frequent cause of a life-threatening pneumonia?
A. Bone marrow transplant patients
B. Hospitalized adults on antibiotic therapy
C. Late-term pregnant women
D. Normal adults in periods of stress
E. Premature infants
F. Preschool children
G. Sexually active adolescents
H. Third-trimester fetuses
Answer
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<7>A 28-year-old HIV-positive male complains of pain on swallowing.
Physical examination is remarkable for white plaque-like material
on his tongue and buccal mucosa, which is scraped and sent to the
laboratory. Based on these findings, and on the laboratory results
, the man is diagnosed with acquired immunodeficiency syndrome (AIDS).
With which of the following agents is the man most likely infected?
A. Candida albicans
B. Cytomegalovirus
C. Herpes simplex I
D. Human herpesvirus 8
E. Human papilloma virus
Answer
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<8>A superantigen is a bacterial product that
A. binds to B7 and CD28 costimulatory molecules
B. binds to the b chain of TCR and MHC class II molecules of APC stimulating T cell activation
C. binds to the CD4 + molecule causing T cell activation
D. is presented by macrophages to a larger-than-normal number of T helper CD4 + lymphocytes
E. stimulates massive amounts of IgG synthesis because of its large size
Answer
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<9>A young adult has progressive intellectual deterioration, weakness,
ataxia, and seizures. Reference laboratory tests demonstrate an
abnormality of an important mitochondrial enzyme. From which of
the following diseases is this person most likely suffering?
A. Adrenoleukodystrophy
B. Central pontine myelinolysis
C. Krabbe's disease
D. Leigh's disease
E. Metachromatic leukodystrophy
Answer
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<10>During a bitterly cold winter, an elderly couple is found dead in
their apartment. All of their windows are closed and their leaky old
furnace is on full. Which of the following is the primary mechanism
by which the toxin involved led to the death of this couple?
A. Decreasing intracellular calcium
B. Inhibition of cytochrome oxidase
C. Inhibition of Na+/K+ ATPase
D. Irreversibly binding to hemoglobin
E. Stimulation of cellular apoptosis
Answer
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<11>A child has a history of recurrent infections with organisms having
polysaccharide antigens (i.e., Streptococcus pneumoniae and Hemophilus
influenzae). This susceptibility can be explained by a deficiency of
A. C3 nephritic factor
B. C5
C. IgG subclass 2
D. myeloperoxidase in phagocytic cells
E. secretory IgA
Answer
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<12>A 32-year-old medical technician had a history of acute eczematous
dermatitis on her hands and wrist in the distribution of the latex gloves
she wore. The skin of her hands was dry, crusted, and thickened. The
eczematous reaction cleared after a 2-week vacation. After 72 hours
back on the job, the eczematous dermatitis returned and continued to
grow worse. Which of the following characterizes the technician's
reaction to the latex gloves?
A. Irritant dermatitis
B. Type I reaction
C. Type II reaction
D. Type III reaction
E. Type IV reaction
Answer
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<13>Cytotoxic T cells induced by infection with virus A will kill target
cells
A. from the same host infected with any virus
B. infected by virus A and identical at class I MHC loci to the cytotoxic T cells
C. infected by virus A and identical at class II MHC loci to the cytotoxic T cells
D. infected with any virus and identical at class I MHC loci to the cytotoxic cells
E. infected with any virus and identical at class II MHC loci to the cytotoxic cells
Answer
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14 .A 22-year-old female college student is brought into
the emergency room by the police, who found her walking back
and forth across a busy street, talking to herself. The young
woman appears to be oriented with respect to person, place,
and time. Her first hospital admission was two months ago
for a similar condition. During a psychiatric interview,
she has difficulty concentrating, and seems to hear voices.
A phone call to her sister provides the additional information
that the girl dropped out of school three months ago and has been
living on the street. Urine toxicology is negative. This patient
is most likely exhibiting the signs and symptoms of
A. schizoaffective disorder
B. schizoid personality disorder
C. schizophrenia
D. schizophreniform disorder
E. schizotypal personality disorder
Answer
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<15>A 4-month-old male presents with twitching of the facial muscles.
He has previously been seen for several severe episodes of Candida
infections. On examination, the child has low-set ears, hypertelorism,
and a shortened philtrum. What additional findings would be likely in
this individual?
A. Absent thymic shadow on chest x-ray
B. Decreased alpha-fetoprotein
C. Decreased IgA levels
D. Elevated IgM levels
E. Prominent telangiectasias around the eyes
Answer
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<16>A 16-year-old high school cheerleader presents with low grade fever,
pleuritic pain and a non-productive cough. Her serum agglutinates
Streptococcus salivarius strain MG. Therapy should include which of
the following?
A. Ampicillin
B. Erythromycin
C. Oxygen and external cooling
D. Penicillin G
E. Ribavirin
Answer
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<17>A 55-year-old male begins group therapy. After the first session, he
befriends one of the other clients, and begins telling her how
extraordinarily intelligent and talented the facilitator is. At
the next session, he and the facilitator disagree. After the
session, he tells his fellow group member that the facilitator
is utterly incompetent and that they should sue for malpractice.
This is an example of
A. displacement
B. fixation
C. reaction formation
D. regression
E. splitting
Answer
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<18>A 5-year-old girl is brought by her parents to the emergency room
because she is complaining of stomach pain. Physical examination reveals
multiple bruises on the child's body in different stages of healing.
X-ray examination of the chest demonstrates two cracked ribs, and the
child says, "Mommy hit me." The parents deny any abuse of their
children. The physician's most appropriate response would be:
A. "I am going to call the police right now."
B. "I must report this situation to Child Protective Services right now."
C. "I need to hospitalize this child for further studies."
D. "I will bind her ribs tonight and you must promise me that you will not strike this child again."
E. "I will bind her ribs tonight and you need to bring her to the outpatient clinic in the morning."
Answer
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<19>A 20-year-old woman sees her baby cousin for the first time. As she
attempts to play with the infant, he begins to cry incessantly. How old
is this baby likely to be?
A. 1-4 months
B. 5-8 months
C. 9-12 months
D. 13-16 months
E. 17-20 months
Answer
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<20>An IgG2 molecule is composed of which of the following?
A. One alpha, one gamma2, and two kappa chains
B. One gamma1 chain and two kappa chains
C. Two gamma1 chains and one kappa and one lambda chain
D. Two gamma1 chains and two kappa chains
E. Two gamma2 chains and two kappa chains
Answer
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<21>Which of the following is the most important costimulatory signal
provided to a T cell from an antigen-presenting cell?
A. B7 molecules interacting with CD 28
B. B7 molecules interacting with LFA- 1
C. ICAM-I interacting with LFA-1
D. LFA-3 interacting with CD 28
E. MHC class II interacting with T cell receptor
Answer
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<22>A febrile 12-year-old child presents with severe right lower quadrant
pain that is interpreted by the attending physician as acute appendicitis.
The patient has also been complaining of joint pain. At laparotomy, the
surgeon notes that the appendix is normal; however, the mesenteric lymph
nodes are markedly enlarged and contain focal areas of microabscess
formation on cut section. This patient is most likely
A. an asthmatic
B. deficient in C1 esterase inhibitor activity
C. HLA-B27 positive
D. leukopenic
E. serologically positive for toxoplasmosis
Answer
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<23>1. Degranulation of mast cells and basophils occurs when allergen binds
to two adjacent IgE antibodies on the membrane of the cell 2. Interleukin
4 released by CD4 helper T cells causes activated B cells to switch from
making IgM to IgE 3. Processed allergen is associated with a class II
molecule on an antigen presenting cell and recognized by CD4+ TH2 cells
4. Prostaglandins and leukotrienes are released 5. The allergen is
phagocytized and processed by a macrophage or a dendritic cell
Based on the numbered list above, which of the following is the
correct sequence of events in the Type I hypersensitivity reaction?
A. 1,2,3,5,4
B. 1,4,3,5,2
C. 1,5,2,3,4
D. 5,3,1,4,2
E. 5,3,2,1,4
Answer
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<24>An antibiotic, such as penicillin, which modifies cell wall synthesis,
tends to be most effective during which phase of bacterial growth in a
closed system?
A. Lag phase
B. Log phase
C. Phase of decline
D. Stationary phase
Answer
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<25>A 57-year-old woman with a history of hypertension and arthritis is
referred to a rheumatologist for evaluation. A complete blood count
(CBC) is normal, and a mini-chem panel shows no electrolyte abnormalities.
Her erythrocyte sedimentation rate (ESR) is elevated, and an antinuclear
antibody test (ANA) is positive. Further antibody studies are performed,
and the results are shown below.
Anti-histones high titer
Anti-double stranded DNA not detected
Anti-single stranded DNA not detected
Anti-SSA not detected
Anti-SSB not detected
Anti-SCI-70 not detected
Anti-Smith not detected
Anit-centromere not detected
Anti-RNP not detected
Which of the following diseases is suggested by these results?
A. CREST syndrome
B. Diffuse form of scleroderma
C. Drug-induced lupus
D. Sjِgren's syndrome
E. Systemic lupus erythematosus
Answer
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<26>A 65-year-old woman is evaluated for symmetrical swelling of the proximal phalangeal joints. Physical examination also reveals large subcutaneous nodules over the extensor surfaces of both arms. Autoantibodies directed against which of the following antigens would most likely be demonstrated by serum studies?
A. Acetylcholine receptor
B. Double stranded DNA
C. Histones
D. IgG
E. Ribonucleoprotein
Answer
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<27>A 6-year-old boy presents to the pediatric clinic with fever and earache. He has just finished an unsuccessful course of amoxicillin. On physical exam, his right tympanic membrane appears injected. Which of the following antimicrobials would be most appropriate to prescribe for this patient?
A. Amphotericin B
B. Bacitracin
C. Cefaclor
D. Erythromycin
E. Sulfamethoxazole
Answer
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<28>A 33-year-old woman is brought into the emergency room by ambulance.
She has been diagnosed as having schizophrenic disorder, disorganized
type, since the age of 17. She has been on antipsychotic medications
since that time, which have controlled her symptoms well. Physical
examination reveals a well-nourished female with a temperature of
103.2 degrees F, BP of 180/99, HR of 97, and copious perspiration.
She is mute, has muscular rigidity and appears to be obtunded.
Which of the following is the most likely diagnosis?
A. Acute dystonia
B. Akathisia
C. Neuroleptic malignant syndrome
D. Parkinsonism
E. Tardive dyskinesia

<29>In a closed system, spores are formed during which of the following
phases of bacterial growth?
A. Decline phase
B. Exponential phase
C. Lag phase
D. Log phase
E. Stationary phase
Answer
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<30>A 14-year-old boy is brought to the emergency department by his
parents because of high fever, headache, and stiff neck for the past
36 hours. He has become confused over the course of the morning. He
uses no medications, has no allergies, and is not sexually active.
On examination, he has a temperature of 38 C, moderate nuchal
rigidity, and marked photophobia. Lumbar puncture is performed,
and the cerebrospinal fluid shows: WBC 3500 with 95% PMNs, elevated
protein, decreased glucose, and gram-positive cocci in pairs and
short chains. By which of the following mechanisms does this
organism mediate its attachment to the respiratory mucosa?
A. Production of a C carbohydrate
B. Production of a hemolytic exotoxin
C. Production of a hyaluronic acid capsule
D. Production of an IgA protease
E. Production of an M protein
Answer
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<31>A 46-year-old woman presents with complaints of feeling as if she
has "sand in her eyes" and reports difficulty swallowing such foods
as crackers or toast. Which of the following pairs of tests would
likely yield positive results in this patient?
A. Anti-centromere antibody and rheumatoid factor
B. Anti-Scl-70 antibody and anti-Smith antibody
C. Anti-Smith antibody and anti-double stranded DNA antibody
D. Rheumatoid factor and anti-double stranded DNA
E. Rheumatoid factor and anti-SS-A antibody
Answer
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<32>A viral organism was isolated from a painful blister on the lip of
a teenage girl. The agent was found to double-stranded, linear DNA and
was enveloped. The patient had a similar sore approximately 2 months
ago. Which of the following is the most likely causative organism?
A. Adenovirus
B. Coxsackie virus
C. Herpes simplex type 1 virus
D. Herpes zoster virus
E. Papilloma virus
Answer
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<33>A British dairy farmer develops fever with chills, myalgias, headache,
skin rash, and vomiting. He is quite ill and is hospitalized. Blood
cultures demonstrate tightly coiled, thin, flexible spirochetes shaped
like a Shepherd's crook. The spirochetes are easily cultured in
serum-enriched nutrient agar. Which of the following organisms
should be suspected?
A. Brucella abortus
B. Brucella melitensis
C. Leptospira interrogans
D. Pseudomonas mallei
E. Pseudomonas pseudomallei

<34>A hospitalized patient develops dysuria and suprapubic pain and is
treated with ciprofloxacin. What is the mechanism of action of this
antibiotic?
A. It inhibits dihydrofolate reductase
B. It inhibits DNA-dependent RNA polymerase
C. It inhibits protein synthesis by binding to the 30s ribosomal subunit
D. It inhibits protein synthesis by binding to the 50s ribosomal subunit
E. It inhibits topoisomerase II (DNA gyrase)
Answer
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<35>A 58-year-old alcoholic man with multiple dental caries develops a
pulmonary abscess and is treated with antibiotics. Several days later,
he develops nausea, vomiting, abdominal pain, and voluminous green
diarrhea. Which of the following antibiotics is most likely responsible
for this patient's symptoms?
A. Chloramphenicol
B. Clindamycin
C. Gentamicin
D. Metronidazole
E. Vancomycin
Answer
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<36>A 36-year-old farmer has been exposed to poison ivy on several
different occasions and usually develops very severe skin lesions.
He enrolls in an immunological study at an urban medical center. A
flow cytometric measurement of T cells reveals values within the
normal range. An increased serum concentration of which of the following
cytokines would decrease the likelihood of a delayed-type hypersensitivity
reaction in this individual?
A. Gamma interferon
B. IL-2
C. IL-4
D. IL-8
E. IL-10
Answer
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<37>A 22-year-old male is evaluated for mitral regurgitation due to mitral
valve prolapse. Examination reveals a tall, slender young man with long
extremities and long tapering fingers. Pupillary dilation followed by
slit-lamp examination reveals bilateral dislocation of the lenses of
the eyes. This patient is potentially at increased risk for development
of
A. aortic dissection
B. Lisch nodules
C. noncaseating granulomata
D. progressive dementia
E. rapidly progressive renal failure
Answer
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<38>A 57-year-old man is seen in clinic for a chronic cough. Chest x-ray
demonstrates a lung mass; bronchoscopy with bronchial lavage and biopsy
reveals a tumor composed of small neoplastic cells with prominent crush
artifact that do not stain with immunohistochemical stains for lymphocyte
common antigen (LCA). Which of the following oncogenes has been
associated with this tumor?
A. bcl-2
B. erb-2
C. L-myc
D. N-myc
E. ret
Answer
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<39>Which of the following features characterizes apoptosis but not
necrosis?
A. Disaggregation of polyribosomes
B. Eosinophilia
C. Inflammation
D. Karyolysis
E. Peripheral aggregation of chromatin
Answer
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<40>A woman who is heterozygous for glucose-6-phosphate dehydrogenase
(G6PD), a polymorphic enzyme transcribed from the X chromosome, develops
chronic myeloid leukemia. Restriction fragment length polymorphism (RFLP)
studies on the tumor cells for G6PD reveal that only a single form of the
enzyme is transcribed. This finding supports which of the following
features of neoplasia?
A. Genetic mutation
B. Monoclonality
C. Mosaicism
D. Oncogene activation
E. Point mutation
Answer
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<41>What is the role of the macrophage during antibody formation?
A. Activation of cytotoxic CD8 T cells
B. Delayed hypersensitivity reaction
C. Lysis of virus-infected cells
D. Processing antigen and presenting it to T helper CD4 cells
E. Synthesis of immunoglobulin
Answer
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<42> The patient shown in the pedigree above did poorly in school,
then became increasingly forgetful and irrational. Over a period of
years, he developed ataxia and began posturing. Eventually, he was
demented and unable to care for himself. At autopsy, extensive cortical
demyelination is observed. Microscopic examination of the areas of
demyelination reveals numerous macrophages containing crystals that
stain a light brown color with toluidine blue. This presentation is
probably due to a deficiency of
A. arylsulfatase A
B. galactocerebroside b-galactosidase
C. glucocerebrosidase
D. hexosaminidase A
E. sphingomyelinase
Answer
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<43>A 46-year-old female with rheumatoid arthritis develops progressively
worsening renal failure. She undergoes diagnostic renal biopsy, revealing
thickening of the mesangial matrix and widened capillary basement
membranes due to deposition of an amorphous, eosinophilic material
that stains with Congo red. The material is shown to be composed of
AA (amyloid-associated) protein fibrils. In which of the following
locations is this protein synthesized?
A. Bone marrow
B. Brain
C. Liver
D. Synovium
E. Thyroid
Answer
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<44>A 38-year-old woman complains of cold, painful fingertips, as well
as difficulty swallowing and indigestion. Physical examination is
remarkable for a thickened, shiny epidermis over the entire body,
with restriction of movement of the extremities, particularly the
fingers, which appear claw-like. Which of the following autoantibodies
is likely to be found in this patient's serum?
A. Anti-DNA topoisomerase I (anti-Scl-70)
B. Anti-double-stranded DNA (ds DNA)
C. Anti-IgG
D. Anti-Sm
E. Anti-SS-A
Answer
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<45>A 67-year-old male smoker presents to his physician for a routine
physical examination. Chest x-ray demonstrates a 2-cm density on the
left side. Laboratory studies are remarkable for a serum sodium of
134 mEq/L. The findings may be attributable to tumor cell secretion
of
A. adrenocorticotrophic hormone (ACTH)
B. antidiuretic hormone (ADH)
C. melanocyte-stimulating hormone (MSH)
D. parathyroid hormone (PTH)
E. vasoactive intestinal polypeptide (VIP)
Answer
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<46>A 28-year-old mother gives birth to her first child. The father
is homozygous Rh D positive and the mother is homozygous Rh D negative.
The baby is born without any complications, but the mother is not given
RhoGAM (anti-Rh IgG) following the delivery. Eighteen months later she
delivers another child, who is anemic, slightly jaundiced, and has an
enlarged spleen and liver. Which type of hypersensitivity best
describes this condition?
A. Atopic disease
B. Cytotoxic disease
C. Delayed hypersensitivity
D. Immediate hypersensitivity
E. Immune complex disease
Answer
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<47>A 24-year-old female has fever, malaise, and a dry, nonproductive
cough. She also complains of headache, muscle aches, and leg pain. Lab
values are significant for elevated cold agglutinins. Which of the
following microorganisms is responsible for her symptoms?
A. Haemophilus influenzae
B. Klebsiella pneumoniae
C. Legionella pneumophila
D. Mycoplasma pneumoniae
E. Streptococcus pneumoniae
Answer
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<48>A 29-year-old news correspondent returns from covering an earthquake
and its aftermath in a third world country. The man feels tired and has
sore muscles, so he consults a physician, who examines him, but decides
not to admit him to the hospital. The man subsequently develops a
disabling illness complicated by severe anemia, pulmonary edema,
renal failure, and shock. Which of the following organisms is the
most likely pathogen?
A. Babesia microti
B. Plasmodium falciparum
C. Plasmodium malariae
D. Plasmodium ovale
E. Plasmodium vivax
Answer
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<49>A 12-year-old boy has a productive cough characterized by large
volumes of foul-smelling sputum. Three years ago, the patient was
diagnosed with pancreatic insufficiency, as evidenced by repetitive
gastrointestinal symptoms of steatorrhea. After culture of the sputum,
colorless, oxidase-positive colonies with a fruity aroma develop on the
agar. The function of which of the following proteins is most likely
inhibited by the bacteria responsible for this boy's infection?
A. A CFTR protein lacking a phenylalanine in exon 10 at position 508
B. A GTP-binding protein involved in the elongation step of protein synthesis
C. A GTP-binding protein similar to the one coupled with a2-adrenergic receptors
D. A GTP-binding protein similar to the one coupled with b-adrenergic receptors
E. A phosphorylation-regulated chloride channel in the apical membrane of epithelial cells
Answer
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<50>Which of the following genes involved in the synthesis of
immunoglobulins are linked on a single chromosome?
A. C gene for gamma chain and C gene for alpha chain
B. C gene for gamma chain and C gene for kappa chain
C. V gene for kappa chain and C gene for the epsilon chain
D. V gene for lambda chain and C gene for kappa chain
E. V gene for lambda chain and V gene for heavy chain

Answer
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Answers
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1>The correct answer is A. This is one of those USMLE-style items where figuring out the diagnosis is the easy part and remembering the basic science details is much tougher. In this case, the patient has all the hallmarks of mononucleosis (the heterophil antibodies should have confirmed your suspicion from the history and physical). Mononucleosis is caused by the Epstein-Barr virus, which, in turn, belongs to the herpesvirus family. The herpesviruses are enveloped viruses with double-stranded DNA. Remember that in addition to Epstein-Barr virus, the herpesvirus family also includes herpes simplex (1 and 2), varicella-zoster (chickenpox, shingles), and cytomegalovirus (infection in immunocompromised). Cytomegalovirus also causes infectious mononucleosis, but in these patients the heterophil test is negative.
There are two families of viruses that are nonenveloped with double-stranded DNA (choice B): papovaviruses and adenoviruses.
There are many families of viruses that are enveloped with single-stranded RNA (choice C): arenaviruses, bunyaviruses, coronaviruses, filoviruses, flaviviruses, paramyxoviruses, orthomyxoviruses, retroviruses, rhabdoviruses, and togaviruses.
Parvoviruses are the only family of DNA virus with single-stranded DNA. They do not have an envelope (choice D).
There are two families of RNA virus that are single-stranded without an envelope (choice E): caliciviruses and picornaviruses.

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2>The correct answer is B. Transformation is the uptake and integration of naked DNA by a bacteria from the environment. Transformation can be induced in the laboratory (a technique used to introduce gene-carrying plasmids into bacteria) or, relatively uncommonly, occurs naturally. Only a few medically important species undergo natural transformation: Haemophilus species, Streptococcus species, Neisseria gonorrhoeae, and Helicobacter pylori.
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3>The correct answer is B. The Stanford-Binet scale is best for younger children (2-4 years old), since it does not rely exclusively on language.
The Denver Developmental Scale (choice A) is used to assess the attainment of developmental milestones in children under 2.
The WAIS-R (Wechsler Adult Intelligence Scale; choice C) is used for individuals aged 17 and over. (Just think, the WAIS-R is rated "R").
The WISC III (Wechsler Intelligence Scale for Children; choice D) is useful for evaluating children aged 6-16.
The WPPSI (Wechsler Preschool and Primary Scale of Intelligence; choice E) is used for children aged 4-6.

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4>The correct answer is D. Squamous metaplasia is a frequent airway response to chronic irritation from cigarette smoking. It represents the replacement of one differentiated tissue with another mature, differentiated tissue. It is believed that the squamous epithelium is more resistant to injurious agents, and so represents an adaptive response.
Dysplasia (choice A) is characterized by pleomorphism (the individual cells may vary widely in appearance) and by loss of normal tissue architecture, rather than by replacement with another mature epithelium (squamous).
Hyperplasia (choice B) refers to growth of a tissue or organ by cellular proliferation.
Malignant transformation (choice C) is the multistep process by which normal cells progress to the "cancer" phenotype. Metaplasia is not malignant transformation, although the stimuli producing metaplasia may also be associated with the development of malignancy.
Necrosis and repair (choice E) typically result in re-epithelialization and/or fibrosis, not metaplasia.
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5>The correct answer is B. The disease is Gaucher disease, which is a glycolipid storage disease in which glucosylceramide accumulates in spleen, liver, and bone marrow. The defective enzyme, a lysosomal hydrolase known as acid beta-D-glucosidase, can be assayed in leukocytes separated from the blood by centrifugation. Interestingly, the defective enzyme can now be supplied intravenously, and strategies for transplantation of the cloned replacement gene are now being developed.
Galactose (choice A) is a sugar. Deficiency of beta-D-glucosidase would not lead to accumulation of galactose.
Glycogen (choice C) is a storage polymer of glucose. It accumulates in various glycogen storage diseases, but has a different appearance than the glycolipid in Gaucher disease.
Homocysteine (choice D) is an amino acid. It does not accumulate in Gaucher disease.
Mineralocorticoids (choice E) are lipids, but do not accumulate in bone marrow.


6>The correct answer is E. This patient has Pneumocystis carinii pneumonia, the most common atypical pneumonia in AIDS patients. The next most common pool of at-risk individuals consists of premature infants.
Bone marrow transplant patients (choice A) would be immunologically compromised, and might be a second at-risk group (behind premature infants), but would not be the first choice on this list.
Hospitalized adults on antibiotic therapy (choice B) might be slightly immunologically compromised or stressed, but are not the major patient pool at risk for this infection in the U.S.
Late-term pregnant women (choice C) are not immunologically compromised and would not be at risk.
Normal adults in periods of stress (choice D) are not particularly susceptible to opportunistic pathogens.
Preschool children (choice F) have normal rates of exposure to P. carinii, as would any adult, but are not susceptible to serious pneumonia with this agent unless they are immunologically suppressed.
Sexually active adolescents (choice G) would have the same infection rates as normal infants and adults, but again would not be susceptible to life-threatening pneumonia. P. carinii is transmitted via aerosols, not sexual activity.
Third-trimester fetuses (choice H) are not susceptible to infection with this fungus, although they may become infected in utero with HIV.
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7>The correct answer is A. Candida albicans produces oral thrush, an AIDS-defining lesion, which is common in acute HIV disease, and becomes increasing common as the CD4 + cell count falls. The lesions are usually painless. Diagnosis is by demonstration of pseudohyphae using a wet smear with confirmation by culture.
Although cytomegalovirus (choice B) is associated with numerous clinical scenarios in the AIDS population, including odynophagia (painful swallowing), it would not produce white plaques on the oral mucosa.
Herpes Simplex I (choice C) produces vesicular lesions occurring in clusters in the oral cavity. There is an increased risk of herpes infections in the AIDS group, but the lesions do not resemble those described in the question.
Human herpesvirus 8 (choice D) is the causative agent of Kaposi's sarcoma, a malignancy arising from endothelial cells that appears as hemorrhagic nodules in different organ systems. It is the most common cancer in the HIV infected population.
Human papilloma virus (choice E) is associated with a variety of lesions, including warts and intraepithelial neoplasias of the vulva and cervix. It is associated with anal condyloma, which can occur in the AIDS population.
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8>The correct answer is B. A superantigen, such as TSST- 1 or staphylococcal enterotoxin, cross-links the variable domain of the TCR b chain to the MHC class II molecule and specifically induces massive T cell activation.
The superantigen does not bind the B7 and CD28 costimulatory molecules (choice A). Instead, the costimulatory molecules bind to each other to stimulate the reaction between the antigen-presenting cell and T cell.
The superantigen does not bind the CD 4 molecules (choice C) but instead binds on the other side of the TCR receptor complex.
The term superantigen has nothing to do with the antigen being presented by macrophages to T cells (choice D).
The term superantigen has nothing to do with its size or its ability to stimulate antibody production (choice E). The term superantigen is used because of its unusual ability to create massive T cell activation by the unique type of binding.

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9>The correct answer is D. Leigh's disease, also known as subacute necrotizing encephalomyelopathy, is a very rare disease that most physicians will never encounter in real life. However, it may show up on the USMLE because it is one of the few examples of diseases involving defects in the mitochondrial DNA rather than the chromosomal DNA. The specific defective enzyme, in at least some cases, is cytochrome oxidase, one of the components of the electron transport system. Muscle and brain are particularly affected. Patients have the presentation described in the question and typically die within several years.
Adrenoleukodystrophy (choice A) is an X-linked disease with abnormal lipid metabolism leading to demyelination in the CNS.
Central pontine myelinolysis (choice B) is characterized by demyelination of the pons (especially the basis pontis) seen after overlying rapid correction of hyponatremia.
Krabbe's disease (choice C) is an autosomal recessive accumulation of cerebrosides in histiocytes in the CNS.
Metachromatic leukodystrophy (choice E) is an autosomal recessive accumulation of sphingolipids in the CNS and elsewhere.
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10>The correct answer is D. This couple died of carbon monoxide poisoning. Carbon monoxide has approximately 240 times the affinity for hemoglobin than does oxygen. In a sense, the hemoglobin-CO dissociation curve is shifted very far to the left compared to the hemoglobin-O2 dissociation curve. This means that the binding of hemoglobin to carbon monoxide is virtually irreversible. (The carbon monoxide that cigarette smokers inhale is cleared only when senescent red cells are phagocytized in the spleen and the hemoglobin is degraded.) In addition, the carbon monoxide shifts the hemoglobin-O2 dissociation curve to the left, making the unloading of O2 to the tissues very difficult. When too much hemoglobin is tied up with carbon monoxide, the person dies. The carbon monoxide-hemoglobin complex has a bright red color; a distinctive feature of carbon monoxide poisoning that can be helpful either at autopsy or in living patients is that this color makes the skin and organs also appear bright cherry red.
Generally, intracellular calcium levels increase, rather than decrease (choice A), with cellular injury or death.
Cytochrome oxidase is inhibited by cyanide (choice B).
Ouabain is an example of a poison that inhibits Na+/K+ ATPase (choice C).
Apoptosis (programmed cell death) is stimulated (choice E) by certain genes (e.g., p53, ced 3,4), glucocorticoids, and aging.
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11>The correct answer is C. IgG is the predominant antibody in the secondary immune response. IgG subclass 2 is directed against polysaccharide antigens and is involved in the host defense against encapsulated bacteria.
C3 nephritic factor (choice A) is an IgG autoantibody that binds to C3 convertase, making it resistant to inactivation. This leads to persistently low serum complement levels and is associated with Type II membranoproliferative glomerulonephritis.
C5 (choice B) is a component of the complement system. C5a is an anaphylatoxin that effects vasodilatation in acute inflammation. It is also chemotactic for neutrophils and monocytes and increases the expression of adhesion molecules. A deficiency of C5a would affect the acute inflammatory response against any microorganism or foreign substance.
Myeloperoxidase in phagocytic cells (choice D) is an element of the oxygen-dependent pathway present in phagocytic cells that effectively kills bacterial cells. The hydrogen peroxide-halide complex is considered the most efficient bactericidal system in neutrophils. Chronic granulomatous disease is associated with a deficiency of NADPH oxidase, which converts molecular oxygen to superoxide (the first step in the myeloperoxidase system). Patients are susceptible to granulomatous infections and staphylococcal infections.
Secretory IgA (choice E) is the immunoglobulin associated with mucous membranes. Selective IgA deficiency is the most common hereditary immunodeficiency. In this disorder, there is failure of the B cell to switch the heavy chain class from IgM to IgA. Patients have an increased incidence of sinopulmonary infections, diarrhea, allergies, and autoimmune diseases.

12>The correct answer is E. Sensitization to latex has become a major healthcare problem. Local skin irritations are common but more severe allergic reactions occur, up to and including rare anaphylactic reactions that are occasionally fatal. The immune responses to latex are immediate-type hypersensitivity (type I) reactions, expressing themselves in minutes, and/or delayed-type hypersensitivity (type IV) reactions, which will express themselves in 48-72 hours. The type I reactions are due to the IgE-mediated sensitivity to latex proteins while the type IV reactions are due to a cell-mediated response to the chemicals that are added in the processing of latex. The type IV response in this circumstance would be referred to as contact dermatitis.
Irritant dermatitis (choice A) can be observed in the early stages of sensitization and can be due to sweating, rubbing, and residual soap. The timing of the reaction after 72 hours points to the type IV reaction rather than an irritant dermatitis.
A type I reaction (choice B) would have been apparent in minutes with characteristic rhinitis, conjunctivitis, urticaria, asthma, angioedema, or anaphylaxis after she put on her latex gloves.
A type II reaction (choice C) is a cytolytic response mediated by an antibody. The type II reaction is observed in the context of hemolytic anemias, thrombocytopenia, neutropenia, etc.
A type III reaction (choice D) is an immune-complex response that sets into motion an inflammatory response.
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13>The correct answer is B. The CD8+ cytotoxic T cells have antigen specific T-cell receptors (TCR) on their membranes that will recognize and bind to self class I antigens. Since the viral peptides are presented as a complex with the self class I antigens, the CD8+ cells can now recognize and react to the virus A peptides. Remember that class I antigens are expressed on all nucleated cells and platelets.
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14>A
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15>The correct answer is A. The clinical findings describe DiGeorge syndrome. Patients clinically present with tetany (usually first noted in the facial muscles) due to hypocalcemia secondary to hypoparathyroidism. The thymus is absent, as are the parathyroid glands, due to failure of development of the 3rd and 4th pharyngeal pouches. Recurrent infections due to defective cellular immunity and abnormal facies are additional features.
Decreased alpha-fetoprotein (choice B) is an amniotic fluid marker for Down's syndrome. Down's syndrome patients have abnormal immune responses that predispose them to serious infections (particularly of the lungs) and to thyroid autoimmune disease. However, there is no defect of the parathyroid glands.
Decreased IgA levels (choice C) describes selective IgA deficiency, which is the most common hereditary immunodeficiency. The syndrome is due to a failure of heavy-chain gene switching in B cells.
Elevated IgM (choice D) is seen in hyper-IgM syndrome. Patients have a high concentration of IgM and normal numbers of T and B cells, but low levels of IgG, IgA, and IgE. Helper T cells have a defect in the surface protein CD40 ligand that interacts with CD40 on the B-cell surface. This results in an inability of the B cell to switch from the production of IgM to other classes of antibodies.
Prominent telangiectasias around the eyes (choice E) are seen as part of the ataxia-telangiectasia syndrome. This is an autosomal recessive disorder, and is also referred to as a chromosomal breakage syndrome. Ataxia-telangiectasia is associated with increased numbers of translocations, especially involving the T-cell receptor loci; the gene for this disorder has been mapped to chromosome 11. Patients have an increased incidence of malignancy.
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16>The correct answer is B. The patient has primary atypical pneumonia caused by Mycoplasma pneumoniae. These organisms are fastidious and difficult to culture in the laboratory, however serodiagnosis can be most helpful. Patients produce one or two heterophile antibodies during the course of the infection: one agglutinates human O+ RBCs in the cold (the cold hemagglutinins) while the other causes the agglutination of a strain of Streptococcus salivarius termed strain MG (the Strep MG agglutinins). Mycoplasma are susceptible to the macrolide family of antibiotics (erythromycin, clarithromycin, etc.). These organisms lack a cell wall, hence they are indifferent to antibiotics that interfere with peptidoglycan synthesis, such as penicillin (choice D) and ampicillin (choice A).
Oxygen and external cooling (choice C) are therapeutic measures that are used in the treatment of severe respiratory diseases such as pneumococcal pneumonia.
Ribavirin (choice E) is used in the treatment of respiratory syncytial virus infection in infants. This is the most common cause of hospitalization for respiratory disease in the very young, probably because aerosol administration of the antiviral compound is best accomplished in a hospital setting.
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17>The correct answer is E. Splitting is a primitive defense mechanism in which objects or people are thought of as either "all bad" or "all good." This defense mechanism is normal in young children, but also occurs in adults with borderline personality disorder (the man in group therapy) or psychosis.
Displacement (choice A) is an unconscious defense mechanism in which one's feelings or desires are unconsciously transferred from their original object to a more acceptable substitute.
Fixation (choice B) refers to an arrest of development at a particular developmental stage. It is generally a partial or incomplete arrest of development, but can contribute to the development of emotional problems if protracted.
Reaction formation (choice C) refers to an unconscious defense mechanism in which the person takes on an attitude or belief that is the opposite of his or her true beliefs and desires.
Regression (choice D) is a return to an earlier (often infantile) stage of development that occurs in many mental illnesses and in normal individuals experiencing tragic or extremely stressful events.
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18>The correct answer is B. All signs, including the child's report, suggest child abuse; however, there can be mitigating circumstances that are present. All states have laws requiring everyone to protect children by reporting the suspicion of child abuse to Child Protective Services. It is the responsibility of this agency to prove or disprove the suspicion, and to establish supervision of the child if abuse is verified.
"I am going to call the police right now" (choice A), is only appropriate if the Child Protective Services is not available immediately.
Choices C, D, and E do nothing to address the issue of the mandatory report of the suspicion of child abuse to the appropriate authorities.
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19>The correct answer is B. The baby is exhibiting stranger anxiety, which normally occurs between the ages of 5 and 9 months.
Let's review some other social milestones that are good to be aware of during clinical work in pediatrics:
Spontaneous smiling begins within several days after birth and disappears by 3 months. Smiling at any face occurs by 2 months, followed quickly by smiling only at familiar faces and when pleased. By 3 months, infants can imitate facial expressions. They laugh at 4 months.
Crying occurs from birth. It peaks at 6 weeks and is most frequent from 4-6 p.m. Colic is defined as crying more than 3 hours a day for more than 3 days a week. It often spontaneously resolves by 4 months. Treatment includes holding, avoiding overstimulation, and antispasmodics.
Separation anxiety occurs between the ages of 10 and 18 months, when the infant is separated from the mother.
Between the ages of 2 months and 2 years, children might show preference for a comforting "transitional object" (e.g., teddy bear), which is usually discarded by age 4, when the transition from dependence on the mother to independence is more complete.
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20>The correct answer is E. IgG molecules contain two gamma heavy chains of a given subtype and two light chains (either kappa or lambda). The 2 in IgG2 indicates the subclass to which the molecule belongs. IgG2 contains two gamma2 chains (since a given B cell can only form one type of heavy chain). The IgG molecule will contain either two kappa chains or two lambda chains, but never one of each (choice C).
A given cell produces immunoglobulin molecules with a single type of heavy chain (compare with choice A).
IgG molecules with gamma1 chains (choices B, C, and D) would be of the IgG1 subclass.
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21>The correct answer is A. The B7 molecule on the cell surface of the antigen-presenting cell reacts with the CD 28 molecule on the T cell surface for maximal costimulatory signals.
The B7 molecule on the surface of the antigen presenting cell reacts only with CD 28 and does not react with LFA-1 (choice B) adhesion molecule.
The ICAM- I on the surface of an antigen presenting cell reacts with the LFA- I (choice C) on the surface of a T cell for the purpose of cell-to-cell adhesion and does not function for costimulation.
The LFA-3 (CD58) is an adhesion molecule on the surface of an antigen presenting cell. It does not react with a CD28 (choice D) costimulatory molecule on the T cell surface.
The MHC class II molecule with its epitope does interact with a specific T cell receptor (TCR) (choice E), but this is not termed costimulatory. However, the interaction does stimulate the T cell to produce interleukins for further cell division
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22>The correct answer is C. Yersinia enterocolitica is the pathogen producing this clinical syndrome. Yersinia is transmitted to patients via the oral route, via contaminated blood products, or by cutaneous inoculation. Patients developing iron overload because of multiple transfusions (i.e., thalassemia patients) are at increased risk of Yersinia infections because some strains are unable to synthesize bacterial iron chelators called siderophores. They can, however, use host-chelated iron stores or the drug deferoxamine (a siderophore produced by Streptomyces pilosus). Yersinia is associated with reactive arthritis following an infection by an enteropathogenic organism. Most patients who develop arthritis express HLA-B27.
A history of asthma (choice A) is not associated with Yersinia infections.
Deficiency in C1 esterase inhibitor activity (choice B) produces the syndrome of angioedema. This is an autosomal dominant trait associated with a deficiency of the serum inhibitor of the activated first complement component. The patients have multiple episodes of edema, affecting skin and mucosal surfaces such as the larynx and the GI tract.
Leukopenia (choice D) is not associated with the clinical scenario in the question. Normal-to-elevated leukocyte counts are the rule in Yersinia infection.
Serological positivity for toxoplasmosis (choice E) is not suggested because toxoplasmosis produces a different clinical picture. Toxoplasmosis can be acquired transplacentally with infected infants exhibiting a wide array of symptoms depending on when the mother was infected during gestation. Toxoplasmosis is also seen in immunocompromised patients such as those with AIDS. In this group of patients, the main organ system involved is the central nervous system.
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23>The correct answer is E. This question illustrates an important point. An allergen or antigen must first be processed by an antigen-presenting cell in an unsensitized host before the CD 4+ T helper cells can react to it. These cells of the TH2 subclass then produce a variety of cytokines including interleukin 4. Interleukin 4 causes the heavy chain switching in the B cells from IgM to IgE. The IgE binds to the surface of mast cells or basophils by the Fc fragment. When the patient is re-exposed to the sensitizing allergen, the IgE binds to the allergen and causes degranulation of the mast cell or basophil.

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24>The correct answer is B. Bacterial growth in a closed system is characterized by four phases:
(1) In the initial lag phase, no growth occurs as the organisms adapt to the new environment.
(2) In the exponential, or log phase, the organisms grow at the fastest rate and antibiotics that interfere with cell growth or division are most likely to be effective.
(3) In the stationary phase, when nutrients have been largely exhausted, organisms tend to stop growing but may remain viable for long periods of time.
(4) In the phase of decline, cell deaths increase due to cell starvation or exposure to toxins.

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25>The correct answer is C. The single finding of high autoantibody titers to histones, without any other autoantibodies, is characteristic of drug-induced lupus. The most commonly implicated drugs are procainamide, hydralazine (given for hypertension), and isoniazid. Patients typically have milder disease than in SLE, and tend to have arthritis, pleuro-pericardial involvement, and, less commonly, rash. CNS and renal disease are not usually observed.
CREST syndrome (choice A) is a milder variant of scleroderma characterized by calcinosis, Raynaud's phenomenon, esophageal dysmotility, sclerodactyly and telangiectasia. Anti-centromere antibodies are diagnostic.
The diffuse form of scleroderma (choice B), also known as systemic sclerosis, causes fibrosis of the skin and internal viscera. This disorder is characterized by anti-SCI-70 and often low titers of many other autoantibodies.
Sjِgren's syndrome (choice D) is characterized by dry eyes and dry mouth. Sjِgren's syndrome in isolation is characteristically positive for anti-SSA and anti-SSB. If it accompanies rheumatoid arthritis, anti-RNP will be positive as well.
Systemic lupus erythematosus (choice E) is a multisystem disorder that is distinguished from drug-induced lupus by the presence of a wide variety of autoantibodies, including anti-double stranded DNA (anti-dsDNA).
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26>The correct answer is D. The disease is rheumatoid arthritis, and the autoantibody is rheumatoid factor, which is usually an IgM or IgG (or less commonly IgA) directed against the constant region of autologous IgG.
Autoantibody directed against acetylcholine receptor (choice A) is a feature of myasthenia gravis.
Autoantibody directed against double stranded DNA (choice B) is a feature of systemic lupus erythematosus.
Autoantibody directed against histones (choice C) is a feature of drug-induced lupus.
Autoantibody directed against ribonucleoprotein (choice E) is a feature of mixed connective tissue disease.

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27>The correct answer is C. The drug of choice for otitis media in children is amoxicillin. But in refractory cases, often due to bacterial resistance, switching to a different drug class is often effective. You must look for another medication that is effective against common organisms responsible for pediatric otitis media, such as Streptococcus pneumoniae (a gram-positive diplococcus) and Haemophilus influenzae (a gram-negative rod). A second-generation cephalosporin, such as cefaclor, should cover both and is the best choice. Consequently, it is commonly used in cases of amoxicillin-resistant otitis media. None of the other choices cover the proper spectrum of organisms.
Amphotericin B (choice A) is an antifungal polyene. It works by binding to ergosterol in the fungal cell membrane, creating an artificial pore. It is used to treat systemic mycoses such as Aspergillus, Blastomyces, Candida, Coccidioides, Cryptococcus, and Histoplasma.
Bacitracin (choice B) is a topical agent used to fight infection with gram-positive organisms. It interferes with cell wall synthesis.
Erythromycin (choice D) is a macrolide antibiotic that binds to the 23s rRNA portion of the 50s subunit of ribosomes, inhibiting release of uncharged tRNA and stopping protein synthesis. Though effective against S. pneumoniae, it is not particularly active against H. influenzae. Note that erythromycin may be used in amoxicillin-resistant otitis media, but only when administered with a sulfonamide such as sulfisoxazole.
Sulfamethoxazole (choice E) is a sulfonamide. It is bacteriostatic and works by inhibiting folic acid synthesis. It resembles p-aminobenzoic acid (PABA) structurally. When combined with trimethoprim (a dihydrofolate reductase inhibitor) it exerts a bactericidal effect and serves as the drug combination of choice for complicated urinary tract infections.

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28>The correct answer is C. Neuroleptic malignant syndrome (NMS) is a potentially fatal condition that can occur at any time during the course of treatment with neuroleptics. The exact etiology is unknown. Excessive muscle contraction produces muscular rigidity, and is also responsible for the high temperature. The obtunded mental state and mutism is characteristic. Muscle relaxants, such as dantrolene, and dopamine agonists, such as bromocriptine, are used in the treatment of NMS.
Acute dystonia (choice A, prolonged contractions of muscle groups), akathisia (choice B, "restless legs" ), and parkinsonism (choice D, pill-rolling tremor and rigidity) are all extrapyramidal side effects that occur early during neuroleptic treatment.
Tardive dyskinesia (choice E) is a late-appearing complication of neuroleptic therapy characterized by perioral and athetoid movements.

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29>The correct answer is E. Spore formation usually occurs during the stationary phase, when cell growth ceases because of a developing lack of nutrients or accumulation of toxins.
During the phase of decline (choice A), the lack of nutrients and the accumulation of toxin become so severe that any viable organisms usually die before they can form spores.
The exponential phase (choices B) and log phase (choice D) are descriptors for the steady state of active growth occurring after the lag phase and before the stationary phase. Many antibiotics are most effective in this period.
The lag phase (choice C) is the initial period of adaptation, prior to growth, which occurs when organisms are introduced to a new environment.
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30>The correct answer is D. This is a case of Streptococcus pneumoniae meningitis. This organism is able to attach to the respiratory mucosa because it has teichoic acids in its envelope, and because it produces an IgA protease. The IgA protease physically cleaves the immunoglobulin molecules, leaving the Fc parts to coat the bacterium. This allows the organisms to bind to the Fc receptors on various mucosal cells.
Streptococcus pneumoniae does not produce a C carbohydrate (choice A), and thus cannot be grouped by the Lancefield terminology.
Although the organism does produce the pneumolysin, which is an alpha-hemolytic exotoxin (choice B), this toxin mediates damage to the respiratory epithelium and inhibition of leukocytic responses, not attachment to the mucosa.
Streptococcus pneumoniae does not produce an hyaluronic acid capsule (choice C); Streptococcus pyogenes does. Most capsules serve to inhibit phagocytosis, rather than to mediate adhesion.
Only the group A Streptococci possess an M protein (choice E), which is used to "type" them and helps inhibit phagocytosis.
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31>The correct answer is E. This patient has Sjِgren's syndrome, which is an autoimmune disease characterized by lymphocytic infiltration of exocrine glands resulting in dry mouth (xerostomia) and dry eyes (keratoconjunctivitis sicca). Patients have an increased risk of malignant lymphoma. Autoantibodies produced include anti-Ro (SS-A), anti-La (SS-B), antinuclear antibodies, and rheumatoid factor.
Choice A: Anti-centromere antibodies are a very specific marker for CREST syndrome. Rheumatoid factor is usually positive in rhe

Usmle-mcq's-6

1>A 25-year-old male presents to his family physician with the following
statement: "Doctor, I can't urinate in public restrooms. I can if
there is no one around, but if I go to the restroom in a movie, an
airport, at the ball park or anywhere that someone else comes in,
I can't urinate. Even if I have already started, it just stops and
I can't get it going until the other person leaves. I am so
embarrassed. What do they think of me if they see I can't
do what every other man can do?" Which of the following
is the most likely diagnosis?
A. Anxiety disorder due to a general medical condition
B. Panic disorder
C. Social phobia
D. Specific phobia
E. Substance-induced anxiety disorder

Answer
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2>Autopsy of an elderly individual who died in a nursing home with no
known genetic diseases reveals small amounts of amyloid deposition
in the heart. Amyloid deposition is not seen in other organs. There
is no history of long-standing inflammatory disease. This type of
amyloid would be most likely to be composed of which of the
following proteins?
A. Amyloid-associated protein
B. Amyloid light chain protein
C. Beta-2-amyloid protein
D. Beta-2-microglobulin
E. Transthyretin
Answer
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3>A family is referred to a genetic specialist because of mild mental
retardation in several of the school-age children. Laboratory evaluation
demonstrates a specific chromosomal breakage site in metaphase studies
of lymphocytes cultured with methotrexate. Which of the following
chromosomes is most likely to be specifically affected?
A. X
B. Y
C. 13
D. 16
E. 21
Answer
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4>A 5-year-old male with no previous medical history is brought to the
ER by his mother because he accidentally ingested a large dose of rat
poison. He is conscious but appears quite agitated. On physical exam,
he is found to have a blood pressure of 110/70 and a heart rate of 90.
Labs are significant for an elevated PT but a normal PTT. The patient
should be immediately treated with
A. atropine
B. flumazenil
C. N-acetylcysteine
D. protamine
E. vitamin K
Answer
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5>A 67-year-old man is evaluated for persistent shooting pains, lower
limb ataxia, and bladder dysfunction. Physical examination demonstrates
small irregular pupils that constrict with accommodation but not in
response to light. A VDRL test is positive. A CT scan of the spinal
cord would most likely demonstrate atrophy of which of the following
structures?
A. Dorsal column
B. Dorsal horn
C. Lateral column
D. Ventral column
E. Ventral horn
Answer
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6>What is the earliest age at which toilet training is likely to be
successful?
A. 10 months
B. 13 months
C. 16 months
D. 19 months
E. 22 months
Answer
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7>A 13-year-old boy is brought to a rural clinic because of poor school
performance. His parents state that he did not begin talking until after
three years of age, and still does not use language as effectively as
his sister, who is 6-years-old. A careful family history reveals that
a maternal grandfather was mildly retarded. The mother has two sisters,
both of whom are apparently normal, but the mother admits that she did
not do well in school, and dropped out at the age of 16. Physical
examination of the child reveals large ears, a long, narrow face,
and large testes. Which of the following genetic mechanisms most
likely accounts for the observed findings in the son?
A. Expanded trinucleotide repeat
B. Genomic imprinting
C. Robertsonian translocation
D. Trisomy 13
E. Trisomy 18
Answer
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8>A 15-year-old is brought to the emergency department in a coma. An alert
ambulance attendant notes that the patient's breath smells like acetone.
This would be most consistent with which of the following?
A. Alcohol intoxication
B. Diabetic hyperosmolar coma
C. Diabetic ketoacidosis
D. Heroin overdose
E. Profound hypoglycemia
Answer
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9>A 28-year-old male with history of mood disorder presents with a decreased
need for sleep, irritability, recklessness, and increased energy. Which of
the following is the most likely additional presenting symptom?
A. Depressed mood
B. Fear of dying
C. Insomnia
D. Racing thoughts
E. Recurrent thoughts and actions that relieve anxiety when
carried out
Answer
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10 A 10-year-old girl who is a suspected victim of child abuse
is referred to a psychologist for evaluation. As part of her
workup, the patient is asked to construct a story based on pictures
. Which of the following psychometric measures was utilized?
A. Minnesota Multiphasic Personality Inventory
B. Myers-Briggs Personality Inventory
C. Rorschach Test
D. Thematic Apperception Test
E. Type A and B Behavior Patterns Test
Answer
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11>
A 65-year-old woman has a long-standing dementing disorder characterized
by deterioration in personality, neglect of personal hygiene, impaired
judgment, and disinhibited behavior. MRI demonstrates severe cortical
atrophy limited to the frontal lobes and anterior two thirds of the
temporal lobes, while the remaining cortex is preserved. No evidence
of recent or remote infarcts is found. Which of the following diagnoses
is most consistent with these pathologic and clinical features?
A. Alzheimer disease
B. Creutzfeldt-Jacob disease
C. Dementia with Lewy bodies
D. Frontotemporal dementia
E. Vascular dementia
Answer
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12>
A 50-year-old woman who works as a paralegal in a law firm comes to her
local doctor because of problems with sleep. The patient says that over
the past several weeks, she hasn't slept well, feels tired, and has had
headaches. She does not smoke or drink alcohol, except on special
occasions, and does not take any medications. The patient's pupils
are 5 mm in size, equal and reactive, with both the direct and
consensual light reflexes intact. Accommodation is unimpaired.
Examination of the visual fields and funduscopy are unremarkable.
Extraocular movements reveal normal conjugate, oblique, and
downward movement, but she is unable to look upwards. No other
abnormalities are found on the neurological examination. Which
of the following is the most likely diagnosis?
A. Acoustic neuroma
B. Astrocytoma in the cerebellum
C. Craniopharyngioma
D. Parasagittal meningioma
E. Pinealoma
Answer
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13>A one-year-old baby presents with increasing flaccid paralysis, lack
of coordination, and hyporeflexia. Over the next several years, the
child's condition deteriorates to a bedridden vegetative state.
Funduscopic examination reveals optic atrophy. Extensive enzymological
studies document a deficiency of arylsulfatase A (cerebroside sulfatase)
in leukocytes. Which of the following is the most likely diagnosis?
A. Gaucher's disease
B. Krabbe's disease
C. Metachromatic leukodystrophy
D. Niemann-Pick disease
E. Tay-Sachs disease
Answer
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14>A 60-year-old male executive with a history of angina pectoris and
depression had bypass surgery the previous day. His depression has
responded well to selective serotonin reuptake inhibitors (SSRIs)
and there is no history of psychosis in the past. He now presents
with confusion, agitation, irritability, and tries to remove his
IV lines. His level of consciousness fluctuates, and at times he
forgets who he is. He is given a neuroleptic drug, and appears
much improved. What is the most likely diagnosis?
A. Adjustment disorder
B. Delirium
C. Dementia
D. Exacerbation of depression with suicidal ideation and
psychotic features
E. Schizophrenia
Answer
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15>A 38-year-old woman with a history of multiple sexual partners is most
at risk for which of the following?
A. Bladder carcinoma
B. Cervical carcinoma
C. Endometrial carcinoma
D. Ovarian carcinoma
E. Rectal carcinoma
Answer
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16>Which of the following chemotherapeutic agents is specific for the M
phase of the cell cycle?
A. Cytarabine
B. Daunorubicin
C. Hydroxyurea
D. Mechlorethamine
E. Vincristine
Answer
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17>A 47-year-old man with a history of type 2 diabetes, depression, and
hypertension presents to the emergency department with spontaneous
priapism. Which of the following drugs is the most likely cause of
his current condition?
A. Atenolol
B. Furosemide
C. Glyburide
D. Paroxetine
E. Trazodone
Answer
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18>Tay-Sachs disease, an autosomal recessive disease caused by a deficiency
of hexosaminidase A, is lethal in childhood. In a population of Ashkenazi
Jews, blood testing shows the frequency of heterozygotes to be 0.1. What
is the probability that the first child of two individuals from this
population with no family history of the disease will have Tay-Sachs?
A. 0.25
B. 0.11
C. 0.0625
D. 0.0025
E. Cannot be calculated from the information given
Answer
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19>A 44-year-old male with a history of polysubstance abuse presents with
nausea, vomiting, increased heart rate, high blood pressure, sweating,
agitation, and weakness. He also complains of seeing monsters on the
wall during the interview. Which of the following best accounts for
this presentation?
A. Alcohol intoxication
B. Alcohol intoxication or cocaine withdrawal
C. Alcohol withdrawal
D. Alcohol withdrawal or cocaine intoxication
E. Cocaine intoxication
F. Cocaine withdrawal
Answer
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20>In which of the following laboratory tests would you expect to find the
greatest disparity in reference intervals between men and (non-pregnant)
women?
A. Mean corpuscular volume
B. Serum alkaline phosphatase
C. Serum ferritin
D. Serum glucose
E. Serum sodium
Answer
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21>A 7-year-old girl is walking across a vacant lot and steps on a nail. The
next day, her foot is sore and the wound appears inflamed. During these
early stages of infection, which of the following compounds exert the
most powerful chemotactic effect on neutrophils, causing them to migrate
into the inflamed area?
A. C5a and IL-8
B. IL-1 and tumor necrosis factor
C. LTC4 and LTD4
D. PGI2 and PGD2
E. Thromboxane and platelet activating factor
Answer
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22>A 23-year-old woman with a history of sickle cell disease presents with
fever and severe bone pain localized to her left tibia. X-ray reveals a
lytic lesion and blood cultures reveal infection. A bone culture grows
gram-negative rods. Which of the following best describes the infecting
organism?
A. It is a facultative intracellular parasite
B. It is a nonmotile facultative anaerobe
C. It is comma-shaped and sensitive to acidic pH
D. It is motile and does not ferment lactose
E. It is motile and oxidase positive
Answer
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23>A 17-year-old girl loses her best friend in an automobile accident. After
the death, she starts writing for hours daily in her diary. This would
most likely be an example of which of the following defense mechanisms?
A. Identification
B. Projection
C. Rationalization
D. Regression
E. Sublimation
Answer
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24>Physical examination of a neonate demonstrates abnormal facies with a
small lower jaw, low-set ears, and a prominent occiput. The feet have a
rocker-bottom deformation, and the infant is hypertonic. Cardiac
evaluation demonstrates a ventricular septal defect. Which of the
following is the average life-span for infants with this neonate's
syndrome?
A. 2-3 months
B. 1-2 years
C. 4-7 years
D. 15-25 years
E. Normal life expectancy
Answer
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25>A biopsy of a brain tumor from a 42-year-old man reveals a glial neoplasm
consisting of atypical astrocytes with scattered mitoses. Besides mitotic
activity, which of the following markers can provide information about
the neoplasm's proliferative activity?
A. bcl-2
B. Glial fibrillary acidic protein (GFAP)
C. Ki-67
D. p53
E. Ubiquitin
Answer
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26>A pharmacologist is determining the pharmacokinetic parameters of a novel
antibiotic in order to determine the proper dosage. The drug is a
weak organic acid with a pKa of 3.0. Assuming a pH of 2.0 in the
stomach, approximately what percent of the drug will be in a form
that can be rapidly absorbed from the stomach?
A. 0.1
B. 1
C. 10
D. 50
E. 90
F. 99
Answer
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27>A 38-year-old woman vacationing in Connecticut is bitten by a tick.
She does not seek medical treatment and eventually develops chronic
arthritis of the knee and hip joints and paralysis of the left facial
muscles. A physical examination during the early stages of the disorder
would most likely have revealed
A. aphthous ulcers in the mouth
B. erythema chronicum migrans
C. flaccid paralysis of limb flexors
D. purpuric lesions in a bathing trunk distribution
E. spastic paralysis of limb extensors
Answer
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28>A 20-year-old man with new onset of seizures and no history of hypertension
is evaluated with a contrast-enhanced CT scan of the head, which
demonstrates a mixed parenchymal and subarachnoid hemorrhage. The
parenchymal hemorrhage is centered over one cerebral hemisphere.
Which of the following is the most likely source of the hemorrhage?
A. Arteriovenous malformation
B. Berry aneurysm
C. Bridging vein
D. Charcot-Bouchard aneurysm
E. Middle meningeal artery
Answer
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29>A baby is born with a small head, small eyes, and 6 fingers on each hand.
Two dimensional echocardiography reveals congenital heart defects.
Which of the following genetic conditions is most likely to be the
cause of this child's presentation?
A. Trisomy 13
B. Trisomy 18
C. Trisomy 21
D. XXY
E. XYY
Answer
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30>A 35-year-old male presents to an infectious disease specialist with
recurrent infections with encapsulated bacterial organisms. The history
indicates that these infections have become apparent in the last
6 months. Laboratory findings indicates that the total immunoglobulin
level exceeded 900 mg/dL with a low CH50 (hemolytic complement) level.
Which of the following is the correct diagnosis?
A. Acquired hypogammaglobulinemia (common variable hypogammaglobulinemia)
B. C3 deficiency
C. Hyper-IgM syndrome
D. Wiskott-Aldrich syndrome
E. X-linked infantile hypogammaglobulinemia
Answer
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31>A researcher develops a specific antibody to the complement component C3b
. Assume that intravenous administration of the antibody prevents the
biological effects of C3b. Administration of the antibody would be
expected to interfere with which of the following biological functions?
A. Decreased appetite
B. Fever
C. Increased collagen synthesis by fibroblasts
D. Increased leukocyte adherence to endothelium
E. Opsonization to facilitate phagocytosis
Answer
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32>A 42-year-old man previously diagnosed with kidney stones complains
of gnawing, burning epigastric pain. On questioning, he also notes
moderate to severe diarrhea. Measurement of the patient's basal gastric
acid output reveals that it is markedly elevated. These symptoms are
likely the result of which of the following neoplastic syndromes?
A. Familial polyposis coli
B. MEN I
C. MEN IIA
D. MEN IIB
E. MEN III
Answer
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33>During the isolation of Met-enkephalin (Tyr-Gly-Gly-Phe-Met) from
post-mortem human brain tissue, researchers find that the peptide
is rapidly degraded by peptidases in 1 minute at 37 C. Detailed
analysis of the peptide cleavage pattern of Met-enkephalin is
investigated with two candidate enzymes. Using the drug bestatin,
the investigators found no detectable Tyr-Gly-Gly-Phe-Met but did
find significant concentrations of Tyr-Gly-Gly. Using thiorphan,
there was no detectable Tyr-Gly-Gly-Phe-Met, but there was a
high concentration of Tyr. Which of the following is the best
conclusion about Met-enkephalin metabolism that can be drawn
from these data?
A. Bestatin inhibits an aminopeptidase, and thiorphan inhibits an endopeptidase in the degradative pathway
B. Bestatin inhibits a carboxypeptidase in the degradative pathway
C. Bestatin inhibits an endopeptidase in the degradative pathway
D. Thiorphan inhibits an aminopeptidase, and bestatin inhibits an endopeptidase in the degradative pathway
E. Thiorphan inhibits an aminopeptidase in the degradative pathway
Answer
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34>The pharmacokinetic properties of a new drug are being studied in
normal volunteers during phase I clinical trials. The volume of
distribution and clearance determined in the first subject are
40 L and 2.0 L/hour, respectively. The half-life of the drug
in this subject is approximately
A. 2 hours
B. 6 hours
C. 14 hours
D. 21 hours
E. 40 hours
Answer
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35>The pregnant mother of a 6-year-old son with glucose-6-phosphate
dehydrogenase deficiency is very worried that her female fetus
will have the disease. The father and mother are clinically normal.
Which of the following is true about her baby?
A. The baby has a 25% chance of clinical disease
B. The baby has a 50% chance of being a carrier
C. The baby has a 50% chance of clinical disease
D. The baby will be a carrier
E. The baby will have clinical disease
Answer
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36>Medical students at a major teaching hospital are routinely assigned
to observe obstetric patients and to assist during delivery. When a male
medical student introduces himself to an obstetric patient, the patient
becomes agitated and requests that no students be present during her
delivery. The patient had been informed, prior to admission, that this
was a teaching hospital and that a student would be assigned to her
case. When informed of the patient's refusal, the attending physician
in charge should
A. ask the patient's husband for his consent
B. assign a female medical student to observe
C. not allow any medical students to observe this patient
D. have the patient's nurse seek permission
E. have the student approach the patient again and explain the necessity for student observation
F. have the student observe in the background as a part of the health care team.
G. meet with the patient and discuss the value of observation in medical training
Answer
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37>A 24-year-old migrant farm worker is rushed to a nearby emergency room
after an accidental exposure to parathion. He is in respiratory distress
and is bradycardic. Which of the following drugs can be given to increase
the activity of his acetylcholinesterase?
A. Atropine
B. Deferoxamine
C. Dimercaprol
D. N-acetylcysteine
E. Physostigmine
F. Pralidoxime
Answer
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38>A 74-year-old woman with multiple myeloma is being treated with high
doses of doxorubicin (Adriamycin). She has also received
cyclophosphamide and prednisone recently. During his examination,
the physician should check the patient for
A. abdominal tenderness
B. bladder distention
C. limitation of movement
D. papilledema
E. pulmonary rales
Answer
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39>A 60-year-old man hospitalized with metastatic colon cancer signs a
DNR order. This means that the medical staff treating him is required
to
A. discontinue narcotic pain medication
B. not attempt CPR in case of cardiac arrest
C. refrain from prescribing future medications
D. withhold parenteral nutrition and IV fluid hydration
Answer
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40>A 27-year-old swimmer who feels insecure about her athletic abilities
harshly criticizes her teammates' techniques. Which of the following
ego defense mechanisms is she displaying?
A. Displacement
B. Projection
C. Reaction formation
D. Repression
E. Sublimation
Answer
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41>In a certain population, the frequency of color-blind males is 1 in 100.
Assuming that the population is in Hardy-Weinberg equilibrium at this
locus, the frequency of color-blind females is approximately
A. 0.0001
B. 0.0005
C. 0.01
D. 0.02
E. 0.025
Answer
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42>A newborn presents with severe acidosis, vomiting, hypotonia, and
neurologic deficits. Serum analysis reveals elevated levels of lactate
and alanine. These observations suggest a deficiency in which of the
following enzymes?
A. Alanine aminotransferase
B. Glutamate dehydrogenase
C. Lactate dehydrogenase
D. Pyruvate carboxylase
E. Pyruvate dehydrogenase
Answer
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43>A 5-year-old boy who has been diagnosed with a mucopolysaccharidosis is
given an IQ test and found to have nearly normal intellectual functioning.
Which of the following are possible diagnoses for this patient?
A. Hunter syndrome or Hurler syndrome
B. Hunter syndrome or Scheie syndrome
C. Hurler syndrome or Sanfilippo syndrome
D. Morquio syndrome or Sanfilippo syndrome
E. Morquio syndrome or Scheie syndrome
Answer
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44>A 72-year-old female patient with Alzheimer's disease, but no other
medical problems, suddenly becomes comatose and dies due to an intracranial
hemorrhage that caused severe damage to her entire left cerebral
hemisphere. There was no evidence or history of trauma. What is the
most
likely cause of this hemorrhage?
A. Epidural hematoma
B. Subdural hematoma
C. Amyloid angiopathy
D. Rupture of berry aneurysm
E. Rupture of Charcot-Bouchard aneurysm
Answer
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45>A 23-year-old man living in a group home for the developmentally
challenged has an IQ of 73. He does not read or write, and communicates
with one or two word utterances. He will not interact with other group
home members, and since birth he has "pulled back" and becomes agitated
when others get physically close to him. In his room, everything is in
a given place; if any of his belongings are moved, he becomes quite
disturbed. Which of the following is the most likely diagnosis?
A. Asperger's disorder
B. Autistic disorder
C. Childhood disintegrative disorder
D. Obsessive compulsive disorder
E. Schizophrenia, catatonic
Answer
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46>Which of the following amino acids is most responsible for the buffering
capacity of hemoglobin and other proteins?
A. Arginine
B. Aspartic acid
C. Glutamic acid
D. Histidine
E. Lysine
Answer
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47>Addition of which of the following exhaustively 14C labeled substrates
would lead to evolution of 14CO2 from a cell-free suspension containing
all the enzymes and substrates required for the synthesis of uridylic
acid?
A. Aspartate
B. Carbamoyl phosphate
C. Glutamine
D. Glycine
E. N10-Formyltetrahydrofolate
Answer
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48>A 54-year-old college professor is diagnosed with colon cancer and has
it resected. Tumor is found extending from the mucosa to the serosal
surface of the colon and in three regional lymph nodes. Histological
examination demonstrates that the tumor is composed of cells with
ovoid, relatively small nuclei that form well-defined glands. Which
of the following best describes this tumor?
A. High stage, high grade
B. High stage, low grade
C. Low stage, high grade
D. Low stage, low grade
Answer
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49> A 52-year-old man presents to his physician after a community health
screening test reveals a fasting glucose of 170 mg/dL. Physical
examination is remarkable for bronze skin pigmentation, hepatomegaly,
splenomegaly, and limitation of motion in the second and third
metacarpophalangeal joints of both hands. A liver biopsy obtained
from the patient is shown above. The man has no known history of
hemolytic anemia, and takes daily multivitamins without minerals.
Which of the following pigments is most likely present in the
man's liver?
A. Bilirubin
B. Carotene
C. Ferritin
D. Lipofuscin
E. Melanin
Answer
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50> Which of the following enzymes is located at arrow 1 in
the electron micrograph above?
A. Carnitine acyltransferase II
B. Fatty acyl CoA synthetase
C. Glucose-6-phosphate dehydrogenase
D. Hexokinase
E. Pyruvate kinase
Answer
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Answers
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(39)

1 The correct answer is C. In the condition described, a person is in a social situation and fears that he or she will not be able to perform in the same manner as most everyone else can. The two most common social phobias concern public speaking and restroom performance (sometimes called "shy bladder".)
Anxiety disorder due to a general medical condition (choice A) is diagnosed when a medical condition precipitates anxiety, e.g., hypoglycemia.
Panic disorder (choice B) is characterized by sudden paroxysms of anxiety. It can strike unexpectedly in uncued situations so it would not occur only when others are present.
Specific phobias (choice D) are unreasonable fears of some identifiable thing, not situation (e.g., elevators).
Substance-induced anxiety disorder (choice E) is diagnosed when anxiety is precipitated by ingestion of a psychoactive substance, e.g., hallucinogens.
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2The correct answer is E. This patient has senile cardiac amyloidosis, which is usually a clinically insignificant condition due to deposition of structurally normal transthyretin (formerly called prealbumin). The transthyretin is a normal serum protein used to transport thyroxin and retinal. In addition to causing senile cardiac amyloidosis, transthyretin, in a mutant rather than normal form, is deposited as amyloid in the familial amyloid polyneuropathies.
Amyloid-associated protein (choice A) is a more common protein deposited as amyloid, and precipitates in secondary amyloidosis associated with underlying chronic inflammatory conditions.
Amyloid light chain protein (choice B) is a common protein deposited as amyloid, and precipitates in amyloidosis related to multiple myeloma and other monoclonal B cell proliferations.
Beta-2-amyloid protein (choice C) is deposited as amyloid in the brain (notably in blood vessels and cerebral plaques) of patients with Alzheimer's disease.
Beta-2-microglobulin (choice D) is a normal serum protein that is deposited in amyloidosis complicating long-term hemodialysis.
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3The correct answer is A. The heritable mental retardation condition associated with chromosomal breakage is fragile X syndrome. The break point is at q27.3 on the X chromosome. The test for this condition involves culturing lymphocytes in either folate-deficient medium or with chemical agents such as methotrexate that tend to break chromosomes. To make the diagnosis, at least 4% of metaphase chromosomes must show the specific break-point on the X chromosome. The percentage of defective X-chromosomes above 4% does not correlate well with the degree of mental retardation. The breakage point is a site of CGG trinucleotide repeats, which tend to expand in successive generations, producing the clinical feature of worsening mental retardation in each generation.
Y chromosome (choice B) damage is not part of fragile X syndrome, but loss of this chromosome is one mechanism of producing 45, X0 (Turner syndrome), characterized by mental retardation.
Trisomy 13 (choice C, Patau syndrome), trisomy 16 (choice D, Edward's syndrome) and trisomy 21 (choice E, Down's syndrome) are all associated with mental retardation, but not chromosomal breakage syndromes.
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4The correct answer is E. As you might have guessed from his elevated PT level, the active ingredient in rat poison is warfarin. It acts as an anticoagulant by interfering with the normal hepatic synthesis of the vitamin K-dependent clotting factors II, VII, IX, and X. The most important adverse effect of warfarin is bleeding. The action of warfarin can be reversed with vitamin K.
Atropine (choice A) is used as an antidote for anticholinesterase toxicity (e.g., ingestion of organophosphates).
Flumazenil (choice B) is used as an antidote for benzodiazepine toxicity (e.g., Valium).
N-acetylcysteine (choice C) is used as an antidote for acetaminophen toxicity.
Protamine (choice D) is used as an antidote for heparin overdose. Note that heparin enhances the activity of antithrombin III, producing its anticoagulant effect. Heparin toxicity would have resulted in an elevated PTT.
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5The correct answer is A. The patient has tabes dorsalis, which is a form of neurosyphilis seen 10 to 25 years or longer after primary disease. The pupils described are Argyll Robertson pupils, and are considered diagnostic for neurosyphilis. Characteristically, the dorsal columns, which contain the ascending tracts for sensory information, become atrophic, probably as a result of damage to the dorsal root ganglion cells.
The dorsal gray horn (choice B) contains neurons that respond to sensory input.
The lateral column (choice C) contains both descending (e.g., lateral corticospinal, rubrospinal) and ascending (e.g., spinocerebellar, spinothalamic) tracts.
The ventral column (choice D) contains both descending (e.g., anterior corticospinal, tectospinal) and ascending (e.g., spinothalamic) tracts.
The ventral horn (choice E) contains lower motor neurons.
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6The correct answer is D. Toilet training is not possible before the age of 18 months because the long nerve fibers have not yet myelinated and sphincter control is not possible. Toilet training should be completed by 4 years of age.
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7The correct answer is A. The features described are typical of the familial form of mental retardation known as fragile X syndrome. This disorder is the second most common heritable cause of mental retardation, second only to Down syndrome. Striking features of this disease are that the clinical features tend to worsen with each successive generation, and that males are usually much more severely affected than females, although nearly 50% of carrier females are at least slightly mentally retarded. The explanation appears to involve a region of DNA on the X chromosome that normally contains 6-54 tandem repeats of the sequence CGG. Carrier females for fragile X syndrome may have up to 200 CGG repeats. Clinically affected individuals have 250-4,000 repeats of the CGG sequence. The greater the number of repeats, the more severe the retardation tends to be. Amplification of premutations to full mutations appears much more likely to occur during oogenesis than spermatogenesis.
Genomic imprinting (choice B) is a phenomenon in which the phenotypic expression of a gene differs if the gene is inherited from the mother, rather than the father. An example of this effect is Angelman ("happy puppet") syndrome, caused by a deletion of band q12 in the maternal copy of chromosome 15. A similar deletion in the paternal chromosome 15 produces a different disease called Prader-Willi syndrome.
A Robertsonian translocation (choice C) causes about 5% of cases of Down syndrome. Generally the mother [typically with genotype 45, XX, -14, -21, +t(14q; 21q)] has normal mentation, but some of her children may carry the translocation in addition to the normal maternal chromosome 21 and normal paternal chromosome 21, producing partial trisomy 21. This form of Down syndrome can appear to be a recessive genetic disease.
Trisomy 13 (Patau syndrome; choice D) is characterized by microcephaly, mental retardation, cleft lip and palate, polydactyly, and rocker-bottom feet. Survival is rare beyond one year.
Trisomy 18 (Edwards syndrome; choice E) is characterized by mental retardation, micrognathia, low-set ears, cardiac defects, renal defects, and rocker-bottom feet. Survival is rare beyond one year.
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8The correct answer is C. The smell of acetone on the breath of a comatose patient is an important, rapid diagnostic clue that strongly suggests ketoacidosis and is usually seen in patients with poorly controlled type 1 diabetes. Other features of diabetic ketoacidosis include high blood glucose, increased serum osmolality, hypovolemia, acidosis, and electrolyte imbalance.
In alcohol intoxication (choice A), the breath will smell like alcohol.
Diabetic hyperosmolar coma (choice B) usually is seen in older patients with type 2 diabetes and is not characterized by ketoacidosis. Since there is no acetone production, there is no specific scent to the breath.
In heroin overdose (choice D), no acetone production occurs and there is no specific scent to the breath.
In hypoglycemic coma (choice E), which can occur in diabetics with insulin overdose, no acetone production occurs and there is no specific scent to the breath.
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9The correct answer is D. The presentation suggests a manic or hypomanic episode of a mood disorder. Patients in a manic episode often have an elated or euphoric mood and racing thoughts. Other symptoms of mania include increased energy, hypersexuality, grandiosity, and increased talkativeness. In some patients, irritability, rather than euphoria, is characteristic.
Depressed mood (choice A) can include anhedonia, decreased self-esteem, energy, concentration, appetite, and libido, as well as increased guilt and sucidality.
An unreasonable fear that one might die (choice B) may be associated with panic disorder. Neurovegetative symptoms including severe anxiety, palpitation, shortness of breath, chest pain, trembling, and paresthesias may also occur.
Despite poor sleep, manic patients do not complain of insomnia (choice C). Their need for sleep is decreased. During depressive episodes, patients complain of insomnia or hypersomnia.
Obsessive-compulsive disorder is characterized by distressing recurrent thoughts (obsession) and actions (compulsion) (choice E) that relieve anxiety when carried out.
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10>***
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11The correct answer is D. Not all dementing disorders manifest with the same clinical features. Although there is considerable overlap in clinical symptomatology among different types of dementias, making clinical diagnosis somewhat problematic, there are classic presentations that allow identification of a specific form of dementia with a high degree of confidence. In this case, the patient has symptoms due to frontal lobe damage, eg, disinhibition, impaired judgment, and personality changes. Furthermore, MRI demonstrates a specific pattern of cortical atrophy, restricted to the frontal lobes and anterior portion of the temporal lobes. This combination points toward a group of dementias called frontotemporal dementia, the most frequent form of which is Pick disease. Other forms of frontotemporal dementia are very infrequent. Remember: frontal symptoms in conjunction with frontotemporal atrophy = frontotemporal dementia/Pick disease.
Alzheimer disease (choice A) is the most frequent form of dementia in industrialized countries. Although symptoms due to frontal damage may be present in Alzheimer disease, they are usually associated with a more generalized impairment of higher neurologic functions, eg, language, memory, and learned movements. In addition, cortical atrophy in Alzheimer disease is widespread and not limited to the frontal and anterior temporal lobes.
Creutzfeldt-Jacob disease (choice B) represents the prototype of prion diseases. Cortical atrophy is not a prominent feature of Creutzfeldt-Jacob disease, which manifests with personality changes, memory loss, and seizures, leading to death after a rapid clinical course (a few months to 1 year).
Dementia with Lewy bodies, also known as diffuse Lewy body disease (choice C), is one of the most common forms of dementia in Western countries, possibly more common than vascular dementia. It is characterized by widespread formation of Lewy bodies in the substantia nigra, limbic cortex, and subcortical nuclei, such as the basal nucleus of Meynert. Extrapyramidal symptoms similar to Parkinson disease manifest in this form of dementia as a result of degeneration of dopaminergic pathways.
Vascular dementia (choice E) is an umbrella term encompassing dementing conditions that arise from pathology of large or small cerebral vessels. It manifests with memory loss associated with focal neurologic symptoms depending on the location of damage. MRI would identify old or recent infarcts, as well as white matter disease. Conditions associated with vascular dementia include the following:
Multi-infarct dementia, which is caused by multiple, scattered brain infarcts secondary to atherosclerosis of large arteries of the circle of Willis and/or carotid arteries.
Binswanger disease, which involves rarefaction of cerebral white matter and is caused by hypertension-related arteriolosclerosis.
Lacunar infarcts, which consist of small (< 1 cm) infarcts in the striatum and thalamus; this condition is related to arteriolosclerosis.
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12The correct answer is E. This patient has a pinealoma. Tumors of the pineal gland compress the vertical gaze center in the tectum of the midbrain. The pineal gland manufactures melatonin from its precursor serotonin; an inadequate supply of melatonin results in insomnia. Tumors of the pineal gland will not compress the cerebral cortex or the rest of the brainstem. Frequently, the only physical sign noted is failure of upward gaze.
An acoustic neuroma (choice A) is a schwannoma of the eighth cranial nerve. It results in deafness, ataxia, and dysarthria. Nystagmus may be present. The gaze centers are not affected.
Astrocytomas of the cerebellum (choice B) are usually seen in children. These tumors present with headache, nausea, vomiting, papilledema, and cerebellar signs such as ataxia, dysarthria, nystagmus, and intention tremor. The gaze centers are not affected.
Craniopharyngiomas (choice C) are usually seen in children. There is failure of growth, headaches, and bitemporal hemianopia.
Parasagittal meningiomas (choice D) usually result in headache, spastic paresis, and urinary incontinence
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13The correct answer is C. There are a number of hereditary sphingolipidoses that have devastating clinical courses. In practice, these diseases may have a variable course and may be difficult to specifically diagnose reliably on clinical grounds alone. The most useful clue to the specific diagnosis in this case is the comment about the deficient arylsulfatase A. Deficiency of this enzyme produces metachromatic leukodystrophy, characterized by accumulation of cerebroside sulfates (galactosyl sulfatide). The cerebroside sulfates accumulate as intra- and extracellular spherical masses that stain metachromatically (purplish rather than bluish) with acid cresyl violet, particularly in the nervous system. The biochemical diagnosis can be made by evaluating cultured cells from a variety of sources, including leukocytes, fibroblasts, and hair bulbs. The most common presentation is that described in the question stem; adolescent and adult variants also occur.
Gaucher's disease (choice A) is a sphingolipidosis caused by deficient beta-glucocerebrosidase.
Krabbe's disease (choice B) is a sphingolipidosis caused by deficient beta-galactocerebrosidase.
Niemann-Pick disease (choice D) is a sphingolipidosis caused by deficient sphingomyelinase.
Tay-Sachs disease (choice E) is a sphingolipidosis caused by deficient hexosaminidase A (alpha subunit).
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14The correct answer is B. Delirium is a common complication of general anesthesia and surgery. It is manifested by acute changes in mental status with waxing and waning level of consciousness, agitation, irritability, and psychosis. Patients usually respond to low-dose neuroleptics to achieve sedation. The course is self-limited.
Any psychosocial or biological stressor can lead to adjustment disorder (choice A). This patient's surgery will restrict his level of functioning, at least in the short term. This will be difficult for a high-functioning individual to accept. Adjustment disorder may present with depressive mood, anxiety, and irritability, but a fluctuating level of consciousness is not a feature of this disorder.
Dementia (choice C) can present with irritability, confusion, and agitation, but usually has an insidious course and affects mainly cognition. In contrast to delirium, it does not have a fluctuating course.
Severe depression can present with irritability, suicidal ideation, and psychotic features (choice D). The patient has a history of depression that responded well to SSRIs and he has no prior history of psychosis. He was motivated to undergo cardiac surgery, so removing his IV lines is unlikely to be a manifestation of suicidal ideation.
Schizophrenia (choice E) presents with bizarre behavior, hallucinations, and delusions. It usually starts at a younger age than the acute symptoms in this patient, and is characterized by progressive deterioration in functioning. It is unlikely for a schizophrenic to achieve the functional level of an executive.
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15The correct answer is B. In a sense, cervical carcinoma can be considered a "sexually transmitted disease," since human papilloma virus (typically strains HPV-16 or HPV- 1 is transmitted venereally. In our culture, HPV-related dysplasia of the cervix is common, even in the 18-28 year old group, and carcinomas of the cervix (more rare now than in the past due to screening and aggressive therapy of dysplasia) can occur in the 35-45 age group. The other cancers listed typically occur in older age groups and are not as clearly related to venereal agents.
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16The correct answer is E. Vincristine (and vinblastine) are Vinca alkaloids that bind to tubulin, a component of cellular microtubules. This leads to disruption of the mitotic spindle apparatus and results in metaphase arrest since the chromosomes are unable to segregate. Since these drugs interfere with mitosis, they are considered cell-cycle specific for the M phase.
Cytarabine (choice A) belongs to the class of antineoplastics that are antimetabolites. This drug class interferes with normal metabolic pathways by competing for enzymatic sites. Specifically, cytarabine (Ara-C) is a pyrimidine nucleoside analog. It interrupts DNA synthesis and function by inhibiting DNA polymerase and incorporating into the DNA or RNA of the cell. As you would expect, this drug is cell-cycle specific for the S phase.
Daunorubicin (choice B) is one of the antibiotic antineoplastic agents (others include dactinomycin, doxorubicin, bleomycin, plicamycin, and mitomycin). These agents work by disrupting DNA functioning. Daunorubicin binds to DNA between base pairs on adjacent strands, resulting in uncoiling of the helix and destruction of the DNA template. While this drug has its maximum effect during the S phase, it is not cell-cycle specific. (Note: the only antibiotic that is cell-cycle specific is bleomycin.)
Hydroxyurea (choice C) works by interfering with ribonucleoside diphosphate reductase, the enzyme responsible for generating the deoxyribonucleotides needed for DNA synthesis. It is S-phase specific.
Mechlorethamine (choice D) is a nitrogen mustard. The nitrogen mustards (mechlorethamine, cyclophosphamide, melphalan, chlorambucil) belong to the larger class of alkylating agents. These agents work by alkylating DNA (along with RNA and proteins). The alkylating agents are generally NOT cell-cycle specific.
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17The correct answer is E. Priapism is characterized by the development of a painful erection for an extended period of time. When untreated, priapism can cause severe penile damage that can culminate in impotence. Administration of the antidepressant drug trazodone has been associated with priapism in a number of patients. In patients with prolonged or inappropriate penile erection, this medication should be discontinued and medical attention should be sought immediately. Injection of alpha-adrenergic stimulants, such as norepinephrine or epinephrine, may be successful in treating the priapism. Surgical intervention is necessary for the treatment of trazodone-induced priapism in many instances.
Atenolol (choice A) is a beta-1 adrenergic antagonist indicated for the treatment of hypertension. This agent is commonly associated with impotence in males.
Furosemide (choice B) is a loop diuretic indicated for the treatment of edema and hypertension; electrolyte abnormalities are the most common side effects seen with this agent.
The sulfonylurea glyburide (choice C) is an oral hypoglycemic agent indicated for the treatment of type 2 diabetes; hypoglycemia is the most common side effect of this agent.
Paroxetine (choice D) is a selective serotonin reuptake inhibitor (SSRI) used for the treatment of depression. This agent is commonly associated with impotence in males.
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18The correct answer is D. Since Tay-Sachs is lethal in childhood, the only adults carrying the gene are heterozygotes. The only mating that will produce progeny with the disease is the mating between two heterozygotes. Using the blood test data, the probability that a random individual is a heterozygote is 0.1. The probability that two heterozygotes will produce a child with Tay-Sachs disease is 0.25. So, the overall probability that two individuals in the population will produce a child with Tay-Sachs is (0.1)(0.1)(0.25), or 0.0025.
Choice A, 0.25, could be obtained if the parents are carriers, so the probability of a Tay-Sachs child is equal to the probability that two heterozygotes will produce a child with the disease, or 0.25.
Choice B, 0.11, could be obtained if both of the parents had a sibling with Tay-Sachs. This would mean that the grandparents must have carried the disease, and that their normal children had a 0.67 chance of carrying the allele. This gives the probability that the parent's child would have Tay-Sachs as (0.67)(0.67)(0.25), or 0.11.
Choice C, 0.0625, is also incorrect. It is the product of (0.25)(0.25).
Choice E incorrectly assumes that because q2, the frequency of the disease, cannot be calculated, and hence the allele frequencies cannot be calculated, that an estimate of the frequency of heterozygotes cannot be made. The problem can be done, however, because the heterozygote frequency (0.1) was given in the question stem.
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19The correct answer is D. This man's presentation can be explained either by alcohol withdrawal or by cocaine intoxication. Nausea, vomiting, sympathetic nervous system activation, and weakness could be produced in either case. Visual hallucinations (seeing monsters) can also be accompanied by tactile and auditory hallucinations. In severe cases, either alcohol withdrawal or cocaine intoxication can cause convulsions.
Alcohol intoxication (choice A and B) is characterized by disinhibition, aggression, impaired attention and judgment, unsteady gait and imbalance, slurred speech, nystagmus, and a decreased level of consciousness.
Other symptoms associated with alcohol withdrawal (choices C and D) include insomnia, headache, and tremors of the tongue, eyelids, and outstretched hands.
Withdrawal from cocaine (choices B and F) is characterized by dysphoria, lethargy, psychomotor retardation or agitation, increased appetite, sleep disturbances, and bizarre or unpleasant dreams.
Other symptoms associated with cocaine intoxication (choices D and E) include grandiosity, paranoid ideation, and pupillary dilatation. Orientation usually remains intact.
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20The correct answer is C. Men have higher reference intervals than women in tests related to iron and hemoglobin (Hb) concentration in blood. The normal reference interval for Hb concentration in women is lower (12.0-16.0 gm/dL) than that for men (13.5-17.5 gm/dL) due to lower serum testosterone levels (testosterone is higher in men and stimulates erythropoiesis) and blood loss during menses. Furthermore, women normally have about 400 mg of iron (as ferritin) in their bone marrow iron stores versus an average of 1000 mg of iron for men. In the absence of inflammation, the small circulating fraction of ferritin (choice C) correlates well with ferritin stores in the bone marrow. Hence, men have different reference intervals for serum ferritin than do women (15-200 ng/mL in men versus 12-150 ng/mL in women).
The mean corpuscular volume (choice A), serum alkaline phosphatase (choice B), serum glucose (choice D), and serum sodium (choice E) are similar in both sexes.
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21The correct answer is A. The most important chemotactic factors for neutrophils are the complement factor C5a and the interleukin IL-8.
The cytokines IL-1 and tumor necrosis factor (choice B) have complex, similar actions, including stimulation of production of many acute-phase reactions, stimulation of fibroblasts, and stimulation of endothelium.
Leukotrienes LTC4 and LTD4 (choice C) cause increased vascular permeability.
Prostaglandins PGI2 and PGD2 (choice D) mediate vasodilation and pain.
Thromboxane and platelet activating factor (choice E) induce platelet changes
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22The correct answer is D. The presence of sickle cell disease in a question stem is usually a significant clue. This question tests if you know that patients with sickle cell anemia are more susceptible to osteomyelitis caused by Salmonella. (The patient's fever, bone pain, and x-ray results indicate osteomyelitis). But note that Staphylococcus aureus (gram-positive coccus) is the most common cause of osteomyelitis in both sicklers and nonsicklers. If it had not been ruled out on bone culture, you should have looked for it in the answer choices. Notice that you were required to know more than just the organism's name; you needed to know its distinguishing features. Choice D describes Salmonella (a gram-negative rod) accurately. Salmonella exists in over 1800 serotypes and is known to contaminate poultry.
A facultative intracellular parasite (choice A) is Legionella, a catalase-positive gram-negative rod. It contaminates air-conditioning cooling towers and causes Legionnaire's disease (a type of pneumonia).
A nonmotile, facultative anaerobe (choice B) is Shigella, a gram-negative rod that does not produce H2S. All Shigella contain an endotoxic lipopolysaccharide. The organism causes bacillary dysentery, with abdominal cramps, fever, and mucoid, bloody diarrhea.
A comma-shaped organism that is sensitive to acidic pH (choice C) is Vibrio cholerae, a gram-negative rod that causes severe enterotoxin-induced diarrhea, with "rice-water" stools and dehydration. The toxin acts by stimulating adenylyl cyclase to overproduce cAMP in the brush border of the small intestine.
A motile and oxidase positive organism (choice E) is Pseudomonas, a gram-negative rod with pili that sometimes produces a polysaccharide slime layer. P. aeruginosa is the prototype and commonly colonizes the lungs of patients with cystic fibrosis. It is associated with blue-green pus.
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23The correct answer is E. Sublimation is the diversion of unacceptable impulses into more acceptable ones. In this case, the girl would like to continue to talk to her best friend, but since that is not possible, she substitutes writing in her diary. An example of sublimation seen fairly frequently in medical settings is the mother whose child died of a disease who becomes active in a state or national organization designed to help families with the disease.
Identification (choice A) is the adoption of characteristics or activities of another person.
Projection (choice B) occurs when someone attributes their own thoughts to a different person.
Rationalization (choice C) is the offering of a false, but acceptable, explanation for behavior.
Regression (choice D) is the adoption of behavior more appropriate to a younger age.
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24The correct answer is A. The syndrome described is Edwards' syndrome (trisomy 1, which is typically characterized by the features noted and additionally causes severe mental retardation, which would not be recognizable in the neonatal period. This disease is relatively common, with an incidence of about 1 in 5000 births (Down syndrome has an incidence of 1 in 2000 births). The average life span is only 2-3 months.
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25The correct answer is C. Ki-67 is a nuclear factor (of uncertain function) whose expression correlates with neoplastic replicative activity. Its expression can be visualized by immunostaining of formalin-fixed, paraffin-embedded sections. Ki-67 labeling correlates with a neoplasm's rate of growth and, therefore, with prognosis.
The bcl-2 gene (choice A) suppresses apoptosis by different mechanisms. Its abnormal activation is involved in the pathogenesis of low-grade lymphomas but not astrocytomas.
GFAP (choice B) is an intermediate cytoskeletal filament (analogue of keratin and vimentin) expressed exclusively by certain types of glial cells, e.g., astrocytes and ependymal cells. Immunohistochemistry for GFAP is used diagnostically to confirm an astrocytic origin of a neoplasm, but gives no information about mitotic or proliferative rate.
The gene p53 (choice D) encodes a protein that blocks the cell cycle when damage to DNA occurs. If the damage is successfully repaired, p53 allows the cell cycle to resume; if not, p53 induces apoptosis, thus eliminating dangerous DNA mutations. Mutations of p53 have been found in the great majority of human neoplasms, including gliomas. However, its expression gives no information concerning neoplastic replicative activity.
Ubiquitin (choice E) is a low-molecular-weight heat-shock protein. Its function is to tag aberrant proteins for degradation. It is present in many abnormal intraneuronal inclusions associated with neurodegenerative disorders, such as Lewy bodies, Pick bodies, and neurofibrillary tangles. It has no relationship with mitotic activity or growth rate.
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26The correct answer is E. First, it is necessary to know that it is the uncharged, lipid-soluble form that can be rapidly absorbed. For an acid: HA <-------> H+ + A-. Therefore, the protonated form is uncharged. The Henderson-Hasselbalch equation is:
pH = pKa - log[protonated form/unprotonated form]
In this case,
2.0 = 3.0 - log [HA/A-]
1.0 = log [HA/A-]
10 = HA/A- = 10/1
HA/(HA + A-) = 10/(10 + 1) = 91%, or approximately 90%
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27The correct answer is B. Lyme disease should be suspected in a patient who is bitten by a tick in the northeastern U.S. Lyme disease was named after a township in eastern Connecticut where the disease was endemic. The disease is spread via a tick vector of the genus Ixodes, which transmits a spirochete that causes a systemic illness. Erythema chronicum migrans is usually the first sign of the illness. This is a large red patch on the buttocks or chest that slowly expands as the center blanches. Generally, patients also have constitutional symptoms, such as fever and chills, during this phase. Stiff neck may develop, along with other signs of meningeal irritation, because of an aseptic meningitis. Other neurologic complications of Lyme disease include Bell's palsy due to involvement of branches of the facial nerve. Arthritis is a prominent feature in about half the patients with Lyme disease. It tends to appear several months after the infection but may persist for several years. The course of the chronic arthritis shows exacerbations and remissions; the most commonly affected joints are the knees and hips. Cardiac abnormalities in Lyme disease include pericarditis and heart block.
Skin manifestations do not include aphthous ulcers (choice A).
Flaccid or spastic paralysis of limbs (choices C and E) does not accompany Lyme disease; neurologic involvement is generally limited to cranial nerves and meningitis.
Purpura (choice D) is associated with vasculitis and does not occur in Lyme disease.
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28The correct answer is A. Arteriovenous malformations are composed of complex tangles of congenitally malformed vessels that typically involve the superficial or deep cerebral hemispheres. There is a slight male predominance, and bleeding typically occurs in adolescence or young adulthood. Symptoms may be those of subarachnoid hemorrhage (headache, increased intracranial pressure) and/or seizures. Surgical resection is usually required for therapy.
Berry aneurysms (choice B) can produce both subarachnoid and parenchymal hemorrhage, but are usually centered near the base of the brain.
Bleeding from bridging veins (choice C) causes subdural hematoma.
Charcot-Bouchard aneurysms (choice D) are small, intraparenchymal aneurysms that are related to hypertension.
Rupture of the middle meningeal artery (choice E) causes epidural hematoma.
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29The correct answer is A. This is Patau syndrome, or trisomy 13. This disorder is also associated with severe mental retardation, abnormal forebrain structures, and death within one year of birth. Patau syndrome has an incidence of 1:6000 births, making it the second most common form of autosomal trisomy.
Trisomy 18 (choice B) is Edwards syndrome, characterized by severe mental retardation, rocker bottom feet (also sometimes seen in Patau syndrome, so be careful!), low-set ears, micrognathia, clenched hands, prominent occiput, and death within one year. Edwards syndrome has an incidence of 1:8000, making it the third most common autosomal trisomy.
Trisomy 21 (choice C) is Down syndrome, and is characterized by mental retardation, flat facial profile, prominent epicanthal folds, simian crease, duodenal atresia, and congenital heart disease. Down syndrome is the most common autosomal trisomy, with an incidence of 1:700.
XXY (choice D) is Klinefelter syndrome and is associated with male hypogonadism and infertility, eunuchoid body habitus, gynecomastia, and lack of male secondary sexual characteristics.
XYY (choice E) is double Y syndrome.