Coagulation Disorders USMLE Step 1 Practice Question
A 6-month-old boy is brought to the emergency department after prolonged bleeding from his circumcision site 3 hours ago. The bleeding has not stopped despite direct pressure for 45 minutes. His mother reports that her two brothers have had similar bleeding problems requiring transfusions as children, but his father's family has no history of bleeding disorders. The patient appears pale but alert. Vital signs show HR 140/min, BP 88/58 mmHg, RR 32/min, temperature 37.3°C, SpO2 97%. Physical examination reveals no hepatosplenomegaly, no petechiae or ecchymoses, and no lymphadenopathy. Laboratory studies are obtained: PT: 13 seconds (normal: 11-14)
aPTT: 68 seconds (normal: 25-35)
Platelet count: 248,000/μL
Fibrinogen: 320 mg/dL (normal)
Bleeding time: Normal Which of the following is the most likely diagnosis?
Answer choices
- AFactor V deficiency
- BHemophilia B (Factor IX deficiency)
- CProthrombin complex deficiency (Factor II/VII/IX/X deficiency)
- DHemophilia A (Factor VIII deficiency)Correct answer
- EVon Willebrand disease
- FFactor XII deficiency
See the full explanation
Get the correct-answer rationale, why each distractor is wrong, the underlying mechanism, and high-yield associations — plus adaptive practice that targets your weak areas — with a free MedBoardPRO account.