Inflammation and Immune Pathology USMLE Step 1 Practice Question
A 41-year-old woman presents with acute dyspnea, hemoptysis, and dyspnea on exertion. Vital signs show BP 148/92 mmHg, HR 118/min, RR 22/min, SpO2 88% on room air. Laboratory studies reveal hemoglobin 9.2 g/dL, elevated creatinine 2.8 mg/dL, and positive anti-glomerular basement membrane antibodies. Chest radiograph shows diffuse alveolar infiltrates. Lung and kidney biopsies demonstrate linear IgG deposition along basement membranes with necrotizing inflammation. No pulmonary nodules noted. Which pathogenic mechanism best explains these findings?
Answer choices
- AType I hypersensitivity with allergic inflammation and tissue edema
- BType III hypersensitivity with immune complex deposition in lungs and kidneys
- CType II hypersensitivity with circulating antibodies binding basement membrane antigensCorrect answer
- DImmune complex disease with complement activation without antibody-basement membrane binding
- EType IV hypersensitivity with T-cell infiltration and delayed tissue damage
- FIgA vasculitis causing similar pulmonary hemorrhage with granular mesangial IgA deposits on immunofluorescence
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