A 60-year-old man with a history of smoking presents with progressive dyspnea and a nonproductive cough. HRCT shows bilateral ground-glass opacities and centrilobular nodules predominantly in the upper lobes. Bronchoalveolar lavage shows pigmented macrophages. He has a 20 pack-year smoking history. Which condition is most likely?
- A Usual interstitial pneumonia (UIP)
- B Desquamative interstitial pneumonia (DIP) ✓
- C Hypersensitivity pneumonitis
- D Pulmonary alveolar proteinosis
Correct answer: B. Desquamative interstitial pneumonia (DIP)
Explanation
Desquamative interstitial pneumonia (DIP) occurs almost exclusively in smokers and is characterized by diffuse accumulation of pigmented macrophages within alveoli (not bronchi). It has a better prognosis than UIP and responds to smoking cessation. UIP (option A) shows basal-predominant honeycombing, not centrilobular nodules. Hypersensitivity pneumonitis (option C) is not smoking-related and shows granulomas.
Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.
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