Inflammation and Immune Pathology USMLE Step 1 Practice Question
A 19-year-old woman presents with fever (39.2Ā°C), petechial rash, and meningitis. Vitals show HR 118/min, BP 94/62 mmHg, RR 22/min, SpO2 98% on room air. Blood cultures pending; CSF shows elevated protein and pleocytosis. Skin biopsy reveals acute inflammation with hemorrhage and fibrinoid necrosis of vessel walls. Notably, neutrophil infiltration is minimal. She denies recent drug exposure. Which hypersensitivity reaction mechanism explains the observed vascular injury pattern?
Answer choices
- AType I hypersensitivity with direct antibody activation of endothelium
- BADCC-mediated antibody-dependent cell-mediated cytotoxicity
- CType III hypersensitivity with immune complex-mediated vasculitisCorrect answer
- DType IV hypersensitivity with cytotoxic T-lymphocyte infiltration
- EType II hypersensitivity with complement-dependent cytotoxicity
- FType I hypersensitivity with mast cell degranulation and histamine-induced vasopermeability
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