Restrictive Lung Disease USMLE Step 1 Practice Question
A 32-year-old male farmer with a 10-year history of hay baling presents to the emergency department with acute-onset dyspnea, productive cough, and malaise that began 6 hours after cleaning moldy hay stored in his barn. He reports similar but milder symptoms 1 week ago that resolved with rest. Temperature is 38.8°C, heart rate 106/min, respiratory rate 26/min, and SpO2 is 91% on room air. Chest X-ray shows bilateral ground-glass opacities and scattered micronodules. Pulmonary function testing demonstrates reduced total lung capacity and decreased DLCO. Complete blood count shows mild lymphocytosis. Which of the following best explains the pathophysiology of his acute pulmonary symptoms?
Answer choices
- AType I hypersensitivity reaction with acute mast cell degranulation in the airways
- BType III hypersensitivity reaction with immune complex deposition in alveolar wallsCorrect answer
- CType IV hypersensitivity reaction with delayed granuloma formation in lung parenchyma
- DAcute pulmonary fibrosis secondary to direct cytotoxic injury from fungal spore inhalation
- EOccupational asthma with bronchial hyperresponsiveness to moldy hay antigens
- FAtypical mycobacterial infection with caseating granuloma formation
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