A 44-year-old woman presents with a 6-month history of progressive exertional dyspnoea, dry cough, and fatigue. HRCT shows bilateral basilar-predominant reticulation, traction bronchiectasis, and honeycombing in a subpleural distribution. Pulmonary function tests show restrictive pattern with reduced DLCO. Bronchoalveolar lavage shows lymphocytes 5%, eosinophils 2%, macrophages 93%. No identifiable cause is found. What is the MOST likely diagnosis?

• A Non-specific interstitial pneumonia (NSIP)
• B Hypersensitivity pneumonitis
• C Usual interstitial pneumonia/Idiopathic pulmonary fibrosis (UIP/IPF) ✓
• D Cryptogenic organising pneumonia (COP)

Explanation

The HRCT pattern of bilateral basilar-subpleural reticulation, traction bronchiectasis, and honeycombing is a typical UIP pattern, which combined with the clinical features (progressive fibrotic ILD in middle-aged patient, no identifiable cause, restrictive spirometry, reduced DLCO) is diagnostic of IPF per ATS/ERS/JRS/ALAT 2022 guidelines without requiring surgical biopsy. NSIP typically shows ground-glass pattern without honeycombing; HP shows centrilobular nodules and upper/mid zone predominance; COP shows consolidation with peribronchovascular distribution.

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

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Written and medically reviewed by the StethoPrep medical team.