A 49-year-old woman who breeds pigeons on her terrace has 8 months of recurrent dry cough and breathlessness, worse several hours after cleaning the loft, with low-grade fever on those days. HRCT shows diffuse poorly defined centrilobular ground-glass micronodules with mosaic attenuation, and expiratory images demonstrate lobular air trapping. No honeycombing. Bronchoalveolar lavage shows 48% lymphocytes. Most likely diagnosis?

• A Chronic hypersensitivity pneumonitis ✓
• B Nonspecific interstitial pneumonia
• C Idiopathic pulmonary fibrosis
• D Pulmonary sarcoidosis

Explanation

Centrilobular ground-glass nodules combined with three-density sign and lobular air trapping on expiratory CT reflect small airway involvement by granulomatous bronchiolitis, the signature of hypersensitivity pneumonitis, supported by avian antigen exposure and marked BAL lymphocytosis. IPF shows basal subpleural honeycombing without air trapping, NSIP gives uniform basal ground glass without centrilobular nodules, and sarcoidosis favors upper-zone perilymphatic nodules with hilar adenopathy rather than this pattern.

Reference: Harrison's Principles of Internal Medicine, 21st ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.