COPD USMLE Step 1 Practice Question
A 49-year-old man with untreated HIV presents with fever (38.5°C), night sweats, and hemoptysis. He reports a 3-month history of progressive weight loss and denies current cough or dyspnea. Vital signs show HR 92/min, RR 18/min, BP 118/76 mmHg, and SpO2 98% on room air. Chest radiograph reveals cavitary lesions in the apical upper lobes. CD4 count is 45 cells/μL. Which anatomic factor best explains the location of these lesions?
Answer choices
- ALower oxygen tension favors growth in the lung apices
- BMycobacteria preferentially invade bronchiolar smooth muscle
- CHigher oxygen tension favors growth in the lung apicesCorrect answer
- DRegional surfactant deficiency causes apical alveolar collapse
- EPulmonary venous congestion is greatest in the upper lobes
- FApical lymphoid tissue provides a sanctuary site for mycobacterial replication
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