28
69.
A 2-year-old boy with a history of recurrent skin abscesses develops posterior cervical lymphadenitis. Results of a flow
cytometry assay measuring reduction of dihydrorhodamine to the fluorescent compound rhodamine (DHR) by resting or
phorbol myristate acetate (PMA)-stimulated neutrophils are shown. Which of the following is the most likely causal
organism?
(A) Bacteroides fragilis
(B)
Mycobacterium tuberculosis
(C) Pseudomonas aeruginosa
(D) Staphylococcus aureus
(E) Treponema pallidum
29
70.
An otherwise healthy 45-year-old man comes to the physician because of a 3-week history of progressive epigastric heartburn
and a 4.5-kg (10-lb) weight loss. The pain tends to be more severe at night and occurs 1 to 3 hours after meals during the day.
He has had similar episodes with lesser intensity during the past year. Abdominal examination shows tenderness to deep
palpation. Test of the stool for occult blood is positive. Endoscopy shows a bleeding 3-cm ulcer in the antrum of the stomach.
A photomicrograph of Steiner silver-stained tissue (400x) from a biopsy of the gastric mucosa adjacent to the ulcer is shown.
Which of the following processes is most likely to be involved?
(A) Elaboration of proteases and urease with local tissue destruction
(B) Hyperacidity and gastric ulcer development
(C) Ingestion of preformed toxins in contaminated well water
(D) Spirochete invasion of gastric cells
71.
A 10-year-old girl is brought to the office by her mother because her school nurse thinks that she may have Marfan
syndrome. She is at the 95th percentile for height and 25th percentile for weight. Physical examination shows a narrow palate
with dental crowding, long slender extremities, and joint laxity. Molecular testing for FBN1 shows a single nucleotide
difference that does not change the amino acid at that locus. Her mother is 163 cm (5 ft 4 in) tall. There is no clinical
evidence of Marfan syndrome in the mother, but she has the same single nucleotide change as the patient. The same
nucleotide change is found in 15 of 200 individuals without Marfan syndrome. Which of the following best describes the
single nucleotide change in the patient and her mother?
(A) It is a disease-causing mutation in the patient and her mother
(B) It
is a polymorphism
(C) It is a sequence variant of unknown significance
(D) It will change the folding of the protein
(E) It will result in a truncated protein
30
72.
A previously healthy 40-year-old woman is brought to the emergency department by her husband because of a 2-day history
of fever, lethargy, and confusion. Her temperature is 38°C (100.4°F), pulse is 80/min, respirations are 18/min, and blood
pressure is 140/90 mm Hg. Physical examination shows scattered petechiae and ecchymoses over the lower extremities.
Neurologic examination shows moderate generalized motor weakness. She is oriented to person but not to place or time.
Laboratory studies show:
Hemoglobin
9 g/dL
Hematocrit
27%
Leukocyte count
8000/mm
3
with a normal differential
Platelet count
15,000/mm
3
Prothrombin time
12 sec (INR=1.1)
Partial thromboplastin time
30 sec
Serum
Urea nitrogen
25 mg/dL
Lactate dehydrogenase
1000 U/L
A peripheral blood smear shows 3+ polychromasia and 3+ schistocytes. Urine and blood cultures grow no organisms. A chest
x-ray shows no abnormalities. Which of the following is the most likely diagnosis?
(A) Acute myeloid leukemia
(B) Autoimmune hemolytic anemia
(C) Thrombotic thrombocytopenic purpura
(D) Toxic shock syndrome
(E) von Willebrand disease
73.
A 17-year-old girl has never had a menstrual period. Physical examination shows a normal female body habitus, normal
breast development, and normal appearing external genitalia. She has no axillary or pubic hair. The patient refuses to have a
pelvic or rectal examination. Which of the following is the most likely explanation for the clinical presentation?
(A) Androgen insensitivity
(B) Congenital adrenal hyperplasia
(C) Ectodermal dysplasia
(D) A psychiatric disorder
(E) A sex chromosome mosaicism
74.
A 12-year-old girl is brought to the physician because of a 2-month history of intermittent yellowing of the eyes and skin.
Physical examination shows no abnormalities except for jaundice. Her serum total bilirubin concentration is 3 mg/dL, with a
direct component of 1 mg/dL. Serum studies show a haptoglobin concentration and AST and ALT activities that are within
the reference ranges. There is no evidence of injury or exposure to toxins. Which of the following additional findings is most
likely in this patient?
(A) Decreased activity of UDP glucuronosyltransferase
(B) Gallstones
(C) Increased hemolysis
(D) Increased serum alkaline phosphatase activity
(E) Ineffective erythropoiesis