A 38-year-old non-smoking woman presents with progressive exertional dyspnoea and a dry cough for 8 months. High-resolution CT shows bilateral ground-glass opacities and reticular changes predominantly in the lower lobes with honeycombing and traction bronchiectasis in a sub-pleural distribution. Pulmonary function tests show a restrictive pattern with reduced DLCO. The most likely diagnosis is:

• A Non-specific interstitial pneumonia (NSIP)
• B Hypersensitivity pneumonitis (HP)
• C Usual interstitial pneumonia (UIP) pattern — likely idiopathic pulmonary fibrosis (IPF) ✓
• D Cryptogenic organising pneumonia (COP)

Explanation

The HRCT pattern with bilateral basal sub-pleural reticular changes, honeycombing, and traction bronchiectasis without upper-lobe predominance is the classical UIP pattern. Combined with progressive restrictive disease and reduced DLCO, this is highly consistent with IPF, which can occur in relatively younger non-smoking women. NSIP lacks honeycombing and shows more uniform ground-glass attenuation. HP typically has upper-lobe predominance and mosaic attenuation with relevant exposure history.

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

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Written and medically reviewed by the StethoPrep medical team.