Inflammation and Immune Pathology USMLE Step 1 Practice Question
A 72-year-old man with a 10-year history of hypertension (previously on no medications) presents to the emergency department with acute severe flank pain, gross hematuria, and dyspnea. He reports his blood pressure has been "very high" for the past 2 months but he ran out of medications. Vital signs show BP 220/145 mmHg, HR 110 bpm, RR 22/min. Serum creatinine is 3.2 mg/dL (baseline 0.9 mg/dL). Urinalysis shows 3+ hematuria with RBC casts and proteinuria. Renal biopsy demonstrates acute cortical necrosis with fibrinoid necrosis of interlobular arteries and arterioles, along with acute tubular necrosis. Immunofluorescence microscopy is negative for immunoglobulin and complement deposition. Which of the following pathologic mechanisms best explains the vascular injury observed in this patient?
Answer choices
- AImmune complex deposition in vessel walls activating complement via the classical pathway
- BDirect endothelial injury from severe hypertension causing acute arterial necrosis with fibrin depositionCorrect answer
- CAntibody-mediated destruction of glomerular basement membrane with secondary vasculitis
- DType II hypersensitivity reaction targeting vascular smooth muscle antigens
- EBacterial lipopolysaccharide-mediated endotoxic injury to the renal vasculature
- FType I hypersensitivity with mast cell degranulation and acute vasodilation
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