Interstitial Lung Disease: Patterns, Causes, and Progression
Interstitial lung disease (ILD) questions test pattern recognition on HRCT, a disciplined search for causes, and prognosis-driven management. The syllabus spans idiopathic interstitial pneumonias, hypersensitivity pneumonitis, connective tissue disease–associated ILD, sarcoidosis, and drug- or exposure-related disease.
Core rules
- A definite usual interstitial pneumonia (UIP) pattern on HRCT - basal and subpleural reticulation, honeycombing, traction bronchiectasis, and no inconsistent features - supports IPF without surgical biopsy when the clinical context fits.
- Multidisciplinary discussion integrating clinical, radiological, and pathological data is the reference standard for ILD diagnosis.
- Antifibrotic drugs (pirfenidone, nintedanib) slow lung-function decline in IPF and are also used in progressive fibrosing ILD; they do not reverse fibrosis.
- Always take an exposure history: birds, mould, hot tubs, occupational dusts, and culprit drugs.
Worked example
A 68-year-old man has 18 months of exertional dyspnoea and bibasal velcro crackles. HRCT shows basal subpleural honeycombing and traction bronchiectasis without ground-glass, nodules, or upper-zone predominance. No connective tissue disease features or exposures are present. This is a definite UIP pattern; in this context it supports IPF. Check baseline spirometry, DLCO, 6-minute walk, and oxygen needs; discuss antifibrotic therapy, vaccination, reflux, and palliative care.
Traps
Calling all basal reticulation “IPF” without excluding connective tissue disease or hypersensitivity pneumonitis; over-reading ground-glass as active inflammation; ignoring DLCO; and treating an acute exacerbation as infection alone.