A 52-year-old farmer with progressive dyspnoea over 8 months has bibasal inspiratory crackles. HRCT shows diffuse centrilobular ground-glass nodules, mosaic attenuation with areas of air trapping on expiratory scans, and relative subpleural sparing. He keeps pigeons at home. Which finding most reliably distinguishes his condition from idiopathic pulmonary fibrosis?

• A Basal predominance of disease
• B Restrictive pattern on spirometry
• C Presence of inspiratory crackles
• D Mosaic attenuation with air trapping on expiratory images ✓

Explanation

Chronic hypersensitivity pneumonitis from avian antigen exposure shows a small airways component: centrilobular ground-glass nodules and three-density mosaic attenuation with air trapping on expiratory HRCT, reflecting bronchiolitis. UIP in IPF shows honeycombing and traction bronchiectasis without air trapping. Basal predominance, crackles and restriction occur in both diseases, so they cannot separate them. Antigen avoidance is the cornerstone of treatment here.

Reference: Fishman's Pulmonary Diseases and Disorders, 6th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.