Restrictive Lung Disease USMLE Step 1 Practice Question
A 45-year-old woman with a 10-year history of systemic sclerosis presents to clinic with progressive dyspnea on exertion over the past 6 months. She reports difficulty climbing stairs but denies orthopnea or paroxysmal nocturnal dyspnea. Vital signs: BP 132/78 mmHg, HR 102 bpm, RR 22/min, SpO2 88% on room air. Physical examination reveals sclerodactyly and mild bibasilar crackles. Pulmonary function tests show FVC 65% predicted, FEV1 58% predicted (FEV1/FVC ratio 89%), and DLCO 38% predicted. High-resolution CT of the chest demonstrates bilateral lower lobe reticular opacities with traction bronchiectasis, esophageal dilation, and no evidence of pulmonary edema. Echocardiography shows mild right ventricular dilatation. Which of the following best explains the disproportionately reduced DLCO relative to the reduction in FVC in this patient?
Answer choices
- APulmonary capillary hemangiomatosis with associated vasculitis
- BScleroderma renal crisis with acute kidney injury causing uremia
- CPulmonary arterial hypertension superimposed on interstitial lung diseaseCorrect answer
- DAcute exacerbation of usual interstitial pneumonia pattern
- EAspiration-related chemical pneumonitis from esophageal dysmotility
- FOccult left ventricular systolic dysfunction with diastolic dysfunction
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