Coagulation Disorders USMLE Step 1 Practice Question
A 16-year-old boy with hemophilia A has been on prophylactic factor VIII therapy (20 units/kg IV twice weekly) for the past 8 years. He presents to the emergency department with acute left knee swelling and severe pain following a minor fall during basketball practice. Vital signs are stable. Physical examination reveals a warm, tender, swollen knee with limited range of motion consistent with hemarthrosis. A stat factor VIII level drawn 30 minutes after receiving a 2500 unit IV bolus of factor VIII concentrate is 8% (desired trough level 20-40% for hemarthrosis). Previous factor VIII levels 6 months ago were therapeutic at similar dosing. He denies fever, rash, or recent infections and reports excellent medication adherence. Which of the following most likely accounts for his inadequate therapeutic response to factor VIII replacement?
Answer choices
- ADevelopment of a factor VIII inhibitor (alloantibody)Correct answer
- BAcute hemophilic arthropathy with synovial inflammation reducing factor VIII bioavailability
- CConcomitant use of an anticoagulant medication causing factor VIII consumption
- DUndiagnosed type 2 von Willebrand disease with reduced factor VIII carrier protein
- EAcute sepsis with disseminated intravascular coagulation and factor VIII depletion
- FHypothermia-induced impairment of factor VIII synthesis by hepatocytes
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.