Inflammation and Immune Pathology USMLE Step 1 Practice Question
A 27-year-old woman with no significant past medical history presents with fever (38.9°C), severe thrombocytopenia (15,000/μL), microangiopathic hemolytic anemia (hemoglobin 7.2 g/dL, schistocytes on blood smear), acute kidney injury (creatinine 2.8 mg/dL), and fluctuating neurologic symptoms. Vital signs show BP 148/92 mmHg, HR 102/min, RR 18/min, SpO2 98% on room air. Coagulation studies and fibrinogen levels are normal. Von Willebrand factor antigen is markedly elevated. Which pathophysiologic mechanism best explains this condition?
Answer choices
- AType I hypersensitivity with mast cell-mediated capillary leak and thrombosis
- BEndothelial cell apoptosis from direct T cell infiltration and cytokine release
- CAntibody-mediated destruction of megakaryocytes reducing platelet production
- DADAMTS13 deficiency allowing uncleaved ultra-large VWF multimers to cause microthrombiCorrect answer
- EImmune complex deposition in the microvasculature triggering complement activation
- FThrombotic activation of the contact pathway with intrinsic factor deficiency leading to platelet consumption
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