USMLE USMLE Certifications USMLE Questions & Answers

• Question 551:

  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 6months. Her temperature is 37.5°C (99.5°F), pulse is 72/min, respirations are 12/min, and blood pressure is 120/66 mmHg. Physical examination shows mildly pale conjunctivae. Pelvic examination shows no abnormalities. Laboratory studies show:

  

  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

  Correct Answer: E

• Question 552:

  

  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

  Correct Answer: B

• Question 553:

  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 mmHg. 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

  Correct Answer: C

• Question 554:

  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

  Correct Answer: A

• Question 555:

  

  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

  Correct Answer: B

• Question 556:

  A couple comes for preconceptional genetic counseling because they both have a family history of αthalassemia. 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%

  Correct Answer: C

• Question 557:

  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

  Correct Answer: C

• Question 558:

  

  A 4-year-old boy from Brazil is brought to the physician because of a 1-week history of painless swelling of his jaw and pressure around his eyes. He is at the 80th percentile for height and weight. Physical examination shows a single 12 × 10-cm lesion in the right side of the jaw with diffuse limits and irregular edges. Photomicrographs of an incisional biopsy specimen of the lesion are shown. Based on these findings, which of the following processes is most likely occurring in the region indicated by the arrows?

  A. Apoptosis

  B. Necrosis

  C. Oncosis

  D. Ostosis

  E. Symptosis

  Correct Answer: A

• Question 559:

  A 33-year-old woman comes to the physician because of a 2-day history of mild nausea, increased urinary urgency and frequency, and constipation. She also has had a 4.5-kg (10-lb) weight loss during the past 2 weeks and a 3-week history of vaginal bleeding. Pelvic examination shows a nodular cervix with an irregular, friable posterior lip, and a rock-hard, irregular, immobile pelvic mass that extends across the pelvis. Examination of biopsy specimens from the cervix and anterior wall of the vagina show well-differentiated keratinizing squamous cell carcinoma. Which of the following best describes the pathogenesis of this patient's disease?

  A. Inactivation of celluar p53

  B. Insertion of viral promotors adjacent to cellular growth factor genes

  C. Specialized transduction

  D. Transactivation of cellular growth factor genes by TAX

  E. Translocation of CMYC to an Ig gene promoter

  Correct Answer: A

• Question 560:

  A 27-year-old man is admitted to the hospital 45 minutes after being involved in a motor vehicle collision. Physical examination shows a sluggish response to stimuli. Neurologic examination shows no other abnormalities. A skull x-ray shows a linear, nondepressed basal skull fracture. Two weeks later, the patient develops polyuria and polydipsia. Laboratory studies show a serum glucose concentration within the reference range, increased serum osmolality, and decreased urine osmolality. Following the administration of desmopressin, urine osmolality increases. The beneficial effect of this drug is most likely due to activation of which of the following?

  A. Adenylyl cyclase

  B. Ca2+ channels

  C. Janus kinase

  D. Serine kinase

  E. Tyrosine kinase

  Correct Answer: A