15
26.
A 30-year-old man is admitted to the hospital for evaluation. He has a 6-week history of colicky abdominal pain and diarrhea
with occasional blood. Three days after admission, he suddenly develops peritonitis and sepsis. Despite appropriate care, he
dies. At autopsy, examination shows a fibrinous exudate over the peritoneal and serosal surfaces, and a punctate opening is
seen in the wall of a thickened loop of small intestine. Several lengths of the small and large intestines are also thickened and
adherent to one another, with marked areas of narrowing. Photomicrographs of a section of the colon are shown. Which of
the following is the most likely diagnosis?
(A) Colon cancer
(B) Crohn disease
(C) Diverticulitis
(D) Ischemic necrosis
(E) Ulcerative colitis
27.
A couple comes for preconceptional genetic counseling because they both have a family history of α-thalassemia. The
woman has a minimally decreased hemoglobin concentration. Genetic studies show a single gene deletion. The man has
microcytic anemia and a two-gene deletion. If the two-gene deletion is in trans (one deletion on the maternal gene and one
deletion on the paternal gene), which of the following percentages of their offspring will have a two-gene deletion?
(A) 0%
(B) 25%
(C) 50%
(D) 75%
(E) 100%
28.
A healthy 22-year-old man participates in a study of glucose metabolism. At the beginning of the study, his serum glucose
concentration is within the reference range. He consumes an 800-calorie meal consisting of protein, fat, and carbohydrates.
He then sleeps through the night without additional food or drink. Twelve hours later, his serum glucose concentration
remains within the reference range. Which of the following mechanisms is most likely involved in maintaining this man's
serum glucose concentration?
(A) Continued gut absorption of calories from the ingested meal
(B) Glucose release from skeletal muscle
(C) Glycogenolysis in the liver
(D) Increased leptin release from adipose tissues
(E) Inhibition of glucagon release by the pancreas
16
29.
A 63-year-old homeless man is brought to the emergency department 1 hour after police found him unresponsive. His
respirations are 30/min. Crackles are heard over the left upper and the entire right lung fields. Despite appropriate lifesaving
measures, he dies. A photomicrograph of a section of the right lung obtained at autopsy is shown. Which of the following
mediators is the most likely cause of the position of the cell indicated by the arrow?
(A) Bradykinin
(B) C5a
(C) Histamine
(D) Nitrous oxide
(E) Prostaglandins
30.
A 16-year-old boy is brought to the physician because of a 3-day history of abdominal pain and vomiting; he also has had
decreased appetite during this period. The pain was initially on the right but now has become generalized. His temperature
is 38.8°C (101.8°F), pulse is 100/min, respirations are 20/min, and blood pressure is 143/83 mm Hg. Abdominal examination
shows guarding with diffuse rebound tenderness. There are no palpable masses. A CT scan of the abdomen shows a
perforated appendix. Examination of peritoneal fluid from this patient will most likely show which of the following
organisms?
(A) Candida albicans
(B)
Citrobacter freundii
(C) Escherichia coli
(D) Staphylococcus aureus
(E) Streptococcus pneumoniae
31.
A 16-year-old boy is admitted to the emergency department because of a knife wound to the left side of his chest. An x-ray of
the chest shows an air-fluid level in the left side of the chest, partial collapse of the left lung, and elevation of the stomach
bubble. The mediastinum is in the midline. Which of the following is the most likely diagnosis?
(A) Hemopneumothorax, not under tension
(B) Hemothorax, not
under tension
(C) Pneumothorax, not under tension
(D) Tension hemopneumothorax
(E) Tension hemothorax
(F) Tension pneumothorax
17
32.
A 20-year-old woman comes to the physician because of a 5-year history of heavy bleeding with menses that often requires
her to change her sanitary pads three times hourly. Menses occur at regular 28-day intervals. She recently sustained a minor
cut to her finger, and the bleeding took longer to stop than usual. She has not had easy bruising or change in weight. She only
takes an oral contraceptive, but she has not been sexually active for the past 6 months. Her temperature is 37.5°C (99.5°F),
pulse is 72/min, respirations are 12/min, and blood pressure is 120/66 mm Hg. Physical examination shows mildly pale
conjunctivae. Pelvic examination shows no abnormalities. Laboratory studies show:
Hemoglobin
10.5 g/dL
Hematocrit
31.3%
Mean corpuscular hemoglobin concentration
28% Hb/cell
Mean corpuscular volume
70 μm
3
Leukocyte count
5500/mm
3
Platelet count
275,000/mm
3
Platelet aggregation studies
normal
Prothrombin time
10.5 sec (INR=1.0)
Partial thromboplastin time
28 sec
A Pap smear shows no abnormalities. Which of the following hematologic disorders is the most likely cause of this patient's
menorrhagia?
(A) Afibrinogenemia
(B) Hemophilia A
(C) Intravascular coagulation
(D) Vitamin K deficiency
(E) von Willebrand disease
33.
A 2-year-old boy is brought to the physician for a well-child examination. He was delivered at term after an uncomplicated
pregnancy. His birth weight was 3500 g (7 lb 11 oz), and Apgar scores were 8 and 10 at 1 and 5 minutes, respectively. At the
age of 15 months, physical examination showed no abnormalities, but he was not yet talking. Both of his parents had learning
difficulties in school, and his mother stopped attending after the 10th grade. He has a maternal uncle with cognitive
disabilities. He is at the 25th percentile for height, 15th percentile for weight, and 90th percentile for head circumference. He
appears irritable, he resists making eye contact, and he is flapping his hands. Which of the following is the most likely cause
of this patient's condition?
(A) Creation of an alternative splice site
(B) Frameshift mutation
(C) Missense mutation
(D) Nonsense mutation
(E) Trinucleotide repeat expansion
34.
A 31-year-old woman with type 2 diabetes mellitus comes to the physician because of an oozing, foul-smelling wound on her
foot for 2 days. Physical examination shows a 4-cm, necrotizing wound with a purplish black discoloration over the heel.
Crepitant bullae producing profuse amounts of serous drainage are seen. A Gram stain of a tissue biopsy specimen shows
gram-positive rods. The causal organism most likely produces which of the following virulence factors?
(A) Endotoxin
(B) Fimbriae
(C) Pneumolysin
(D) Polysaccharide capsule
(E) α-Toxin