Synopsis
Use a disciplined clinical, exposure, radiological and physiological framework to recognise interstitial lung disease, identify emergencies and reach a defensible multidisciplinary diagnosis.
- ILD is an umbrella description, not a final diagnosis: classify the clinical context, HRCT pattern and likely cause before selecting treatment.
- Take an exposure history that reaches beyond occupation to birds, mould, hot tubs, humidifiers, hobbies, dusts, vaping, radiotherapy and every prescribed or non-prescribed medicine.
- Search actively for connective-tissue disease through Raynaud phenomenon, inflammatory joints, rashes, proximal weakness, sicca symptoms, dysphagia and mechanic's hands.
- A normal chest radiograph does not exclude early ILD; persistent compatible symptoms or basal crackles justify spirometry, gas transfer and specialist imaging consideration.
- HRCT pattern language guides probability but does not replace context: usual interstitial pneumonia can occur in IPF, connective-tissue disease, chronic hypersensitivity pneumonitis and asbestosis.
- Serial forced vital capacity, gas transfer, symptoms and exertional oxygenation reveal trajectory more reliably than a single measurement.
- Clubbing and fine late-inspiratory basal crackles support fibrotic lung disease, but their absence does not safely rule it out.
- Diagnosis should be reviewed in an ILD multidisciplinary meeting when clinical, radiological or pathological evidence is uncertain or treatment carries material risk.
- Acute deterioration is a syndrome requiring a fresh differential; infection, pulmonary embolism, cardiac failure and treatment toxicity are often more actionable than acute exacerbation.
- Management includes diagnosis-specific therapy, smoking cessation, vaccination, rehabilitation, oxygen assessment, symptom control, advance care planning and timely transplant discussion where appropriate.
Key red flags
A rapid fall over days with new bilateral opacities, marked desaturation or increased work of breathing is an emergency. Consider infection, embolism, oedema, pneumothorax, haemorrhage, drug toxicity and acute exacerbation.
Disproportionate breathlessness, syncope, chest pain, raised jugular venous pressure, oedema or a gas-transfer reduction out of proportion to volumes warrants urgent evaluation for pulmonary vascular disease.
Haemoptysis, focal persistent opacity, unilateral effusion, pleural nodularity, unexplained weight loss or asymmetric lymphadenopathy should trigger the relevant urgent cancer pathway rather than being absorbed into an ILD label.
Investigation priorities
Identify cause, tempo, comorbidity and immediate severity.
Management branches
Persistent breathlessness, cough, crackles or imaging suggests diffuse parenchymal lung disease.
- Assess physiological stability and oxygenation first; arrange same-day care for acute hypoxaemia, haemodynamic compromise, haemoptysis or rapidly progressive symptoms.
- Construct symptom, medicine and lifetime exposure timelines, examine for connective-tissue and sarcoid features, then obtain chest imaging, full lung function and targeted blood tests.
- Refer to a specialist ILD service for protocolled HRCT interpretation and multidisciplinary integration; do not call a pattern 'idiopathic' before credible causes are examined.
- Agree whether further sampling would change treatment, record diagnostic confidence and uncertainty, and provide the patient with a named contact and safety-net.