Coagulation Disorders USMLE Step 1 Practice Question
A 63-year-old man is recovering after hip replacement surgery and has been receiving unfractionated heparin. On hospital day 6 he develops pain and swelling in the left calf. Laboratory studies show that his platelet count has fallen from 260,000/mm3 to 95,000/mm3. Which of the following best describes the pathogenesis of this condition?
Answer choices
- ADeficiency of ADAMTS13 leading to microthrombi
- BAutoantibodies against factor VIII causing prolonged PTT
- CAutoimmune destruction of GpIIb/IIIa in the spleen
- DDirect marrow suppression by heparin
- EIgG antibodies against the heparin-platelet factor 4 complex causing platelet activation and thrombosisCorrect answer
- FImmune complex deposition in small vessels leading to complement-mediated platelet consumption
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