COPD USMLE Step 1 Practice Question
A 36-year-old nonsmoker presents with progressive dyspnea and decreased exercise tolerance over 2 years. Vital signs show BP 128/82, HR 102, RR 24, SpO2 92% on room air. CT chest reveals panacinar emphysema predominantly affecting lower lobes. Laboratory studies show elevated transaminases (AST 68 U/L, ALT 72 U/L) and serum alpha-1 antitrypsin level 57 mg/dL. He denies tobacco or occupational exposures. Which mechanism best explains these findings?
Answer choices
- AInactivation of surfactant by plasma proteins
- BDeposition of ferruginous bodies in the interstitium
- CAutoimmune destruction of bronchial smooth muscle
- DDynein arm defect in respiratory cilia
- EUnopposed neutrophil elastase activity due to low alpha 1 antitrypsinCorrect answer
- FSmoking-related centrilobular upper lobe emphysema
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