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

• 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)

• 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 all of:

• Persistent exertional breathlessness

• A persistent cough

• Bibasal inspiratory crackles

• Clubbing

• Normal or restrictive spirometry

Timely referral matters most: 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