🫁 Diffuse Parenchymal Lung Disease (DPLD), also called Interstitial Lung Disease (ILD), refers to a group of >200 conditions causing
inflammation and fibrosis of the pulmonary interstitium and alveoli.
The result is progressive breathlessness, reduced gas exchange, and eventual respiratory failure.
📖 About
- Over 200 causes; many idiopathic or poorly understood.
- Fibrosis disrupts gas transfer at the alveolar–capillary membrane.
- Some cases are reversible (e.g. hypersensitivity pneumonitis), but many are progressive (e.g. IPF).
🧬 Aetiology & Risk Factors
- Genetic: MUC5B variant → associated with milder IPF.
- Environmental: smoking 🚬, dusts, asbestos, silica, coal.
- Drugs: methotrexate, bleomycin, amiodarone, nitrofurantoin, statins.
- Radiation therapy.
🔑 Key Types
- Idiopathic pulmonary fibrosis (IPF)
- Sarcoidosis (non-caseating granulomas)
- Connective tissue disease–associated ILD (RA, Scleroderma, Polymyositis, Dermatomyositis, SLE, IBD)
- Hypersensitivity pneumonitis
- Farmer’s lung 🌾 (mouldy hay)
- Bird fancier’s lung 🐦 (avian proteins)
- Cryptogenic organising pneumonia
- Pneumoconiosis
- Asbestosis
- Silicosis
- Coal workers’ pneumoconiosis
🩺 Clinical Features
- Progressive exertional dyspnoea & dry cough.
- Reduced chest expansion, fine “Velcro” crackles at lung bases.
- Weight loss, fatigue, eventual hypoxaemia.
- Clubbing → esp. IPF & asbestosis.
- Extra-pulmonary clues: rash, synovitis, erythema nodosum, Raynaud’s.
- Haemoptysis, chest pain, purulent sputum are unusual → think alternative diagnosis.
🔬 Investigations
- Bloods: FBC, U&E, CRP/ESR, autoantibody panel (ANA, ENA, RF, anti-CCP, anti-Jo1, SCL-70), ACE (sarcoid).
- CXR: Reticular “net-like” opacities.
- HRCT: Gold standard → ground glass, reticulation, honeycombing, traction bronchiectasis, subpleural fibrosis.
- Spirometry: Restrictive picture – ↓FVC, ↓FEV1 (ratio preserved), ↓DLCO.
- BNP: if pulmonary hypertension/CCF suspected.
- Lung biopsy: (surgical or transbronchial) – may show Usual Interstitial Pneumonia (UIP) in IPF.
- Allergen testing: RAST if hypersensitivity suspected.
🧾 Differential Diagnosis
- Bronchiectasis
- Heart failure (can mimic on CXR/echo)
🔬 Pathology & Distribution
- Honeycomb lung = end-stage fibrosis.
- Granulomas = sarcoidosis, HP, TB.
- Upper lobe → “SCHART” mnemonic: Silicosis, Sarcoid, Coal workers, Histiocytosis, Ankylosing spondylitis, Radiation, TB.
- Lower lobe → “RASIO” mnemonic: RA, Asbestosis, Scleroderma, IPF, Other drugs.
💊 Management
- Supportive: Oxygen therapy, pulmonary rehabilitation, vaccination.
- IPF: Antifibrotics (Pirfenidone, Nintedanib) – slow decline but do not reverse disease.
- Sarcoidosis: Steroids ± methotrexate/azathioprine.
- CTD-associated ILD: Immunosuppressants (steroids, mycophenolate, cyclophosphamide).
- Hypersensitivity pneumonitis: Antigen avoidance + steroids.
- Lung transplantation for end-stage disease.
📚 References
