Coagulation Disorders USMLE Step 1 Practice Question
A 35-year-old woman presents with confusion, fever, and dark urine. Vital signs show temperature 38.9°C, blood pressure 108/72 mmHg, heart rate 102/min, respirations 18/min, and SpO2 98% on room air. Examination reveals diffuse petechiae. Laboratory studies show hemoglobin 8.1 g/dL, platelets 19,000/mm³, creatinine 1.9 mg/dL, and elevated lactate dehydrogenase. Peripheral smear demonstrates schistocytes. PT and PTT are normal. She denies recent antibiotic use. Which of the following best explains the pathogenesis?
Answer choices
- AAutoantibody against ADAMTS13 causing large von Willebrand multimersCorrect answer
- BDefect in glycoprotein Ib mediated platelet adhesion
- CConsumption of fibrinogen from tissue factor activation
- DImmune destruction of platelets after heparin exposure
- EDeficiency of factor VIII due to inherited mutation
- FEndothelial injury from complement activation via the alternative pathway with C5b-9 complex deposition
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