Inflammation and Immune Pathology USMLE Step 1 Practice Question
A 52-year-old man with no smoking history presents with 8 weeks of progressive dyspnea, low-grade fever, and fatigue. Chest X-ray shows bilateral hilar lymphadenopathy with scattered nodular opacities in both upper lobes. Laboratory studies reveal serum calcium 11.2 mg/dL, ACE level 68 U/L (normal <40), and elevated angiotensin-converting enzyme. Bronchoalveolar lavage demonstrates increased CD4+ T lymphocytes with a CD4:CD8 ratio of 6:1 and occasional epithelioid histiocytes. Transbronchial biopsy shows non-caseating granulomas without acid-fast bacilli or fungal organisms on special stains. Which of the following best describes the primary immunologic mechanism underlying this patient's lung pathology?
Answer choices
- AType II hypersensitivity reaction with anti-basement membrane antibody deposition
- BType III hypersensitivity with circulating immune complex deposition in pulmonary vasculature
- CType IV hypersensitivity with Th1 and Th17-mediated granuloma formationCorrect answer
- DType I hypersensitivity with mast cell degranulation and eosinophilic inflammation
- EInnate lymphoid cell dysregulation with neutrophil-predominant inflammation
- FAntibody-mediated complement activation with C3 glomerulonephritis
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