Restrictive Lung Disease USMLE Step 1 Practice Question
A 38-year-old woman with systemic lupus erythematosus presents to the pulmonary clinic with a 3-week history of progressive dyspnea and intermittent hemoptysis. She denies chest pain, orthopnea, or lower extremity edema. Vital signs: HR 98/min, BP 132/86 mmHg, RR 20/min, SpO2 96% on room air. Physical examination reveals clear lung fields bilaterally and no peripheral edema. Laboratory studies show positive ANA and anti-dsDNA antibodies. Chest X-ray demonstrates bilateral ground-glass opacities in the lower lobes with clear upper lobes. Pulmonary function testing reveals FVC 78% predicted, FEV1 80% predicted, FEV1/FVC ratio 0.85, and DLCO 62% predicted. Which of the following best explains the disproportionate reduction in DLCO relative to the reduction in FVC?
Answer choices
- APulmonary fibrosis with progressive loss of alveolar surface area
- BDiffuse alveolar hemorrhage with hemosiderin-laden macrophagesCorrect answer
- CPulmonary arterial hypertension from chronic hypoxemia
- DShrinkage of the pulmonary capillary bed secondary to acute interstitial edema
- EAcute respiratory distress syndrome from SLE-associated infection
- FPulmonary embolism complicating antiphospholipid syndrome
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