Interstitial Lung Disease

🧭 When to suspect

Interstitial lung disease (ILD) is an umbrella term for over 200 disorders that injure the lung parenchyma – the alveolar walls and surrounding interstitium – producing inflammation, fibrosis, or both. The conditions a GP meets most are idiopathic pulmonary fibrosis (IPF), connective tissue disease-associated ILD, hypersensitivity pneumonitis, sarcoidosis, and drug-induced and occupational/environmental fibrosis.

Suspect ILD in any adult with persistent, unexplained exertional breathlessness and/or a chronic dry cough that has not settled with treatment for the common mimics – chest infection, asthma, chronic obstructive pulmonary disease (COPD) or heart failure. The cardinal examination clue is bilateral fine end-inspiratory ‘Velcro’ crackles, often with finger clubbing. NICE advises actively considering IPF in a patient over 45 with persistent exertional breathlessness, a persistent cough, bibasal inspiratory crackles, clubbing, and normal or restrictive spirometry.

The single most important primary-care action is timely referral: ILD is frequently mistaken for recurrent infection or cardiac failure, and diagnostic delay is associated with worse outcomes. Diagnosis rests on high-resolution CT and a specialist multidisciplinary team (MDT) – a normal chest X-ray or normal spirometry does not exclude it.

Source: NICE CG163 · British Thoracic Society