Interstitial Lung Disease (ILD)

Types

• Idiopathic Pulmonary Fibrosis (IPF)

  • Typically age >50, associated with smoking, gastro-oesophageal reflux disease (GORD)

  • Antifibrotic agents (pirfenidone, nintedanib) may slow disease progression

• Connective Tissue Disease–Related ILD (CTD-ILD)

  • Common in RA, SLE, systemic sclerosis

  • May respond to immunosuppressive therapy (e.g. mycophenolate mofetil, cyclophosphamide)

• Pneumoconioses

  • From occupational exposures: Asbestos, silica, coal dust

• Hypersensitivity Pneumonitis

  • Inhaled organic allergens (e.g. bird proteins, mould) → alveolar inflammation

• Drug-Induced

  • Amiodarone, methotrexate, nitrofurantoin can all cause ILD

• Smoking-Related

  • Includes respiratory bronchiolitis–ILD and Langerhans cell histiocytosis (often younger smokers)

Presentation

• Dry cough, progressive dyspnoea

• Velcro crackles on auscultation, clubbing (particularly in IPF)

• Signs of underlying CTD if relevant (rash, Raynaud’s, arthralgias)

• Specialist referral for HRCT (high-resolution CT) to confirm pattern; DLCO helps differentiate parenchymal from extraparenchymal causes

• Vaccinations (influenza, pneumococcal) recommended due to increased infection risk

Investigations

1. Initial

   • Pulse oximetry → check resting SpO₂ and possible desaturation on exertion

   • Spirometry → restrictive pattern: ↓FVC with preserved or increased FEV₁/FVC ratio

   • CXR → reticular or reticulonodular opacities, possible honeycombing

2. Specialist

   • HRCT → critical for diagnosis and pattern differentiation (e.g. UIP, NSIP)

   • Autoimmune markers (ANA, RF) if CTD suspected

   • DLCO (diffusing capacity) → often reduced in ILD

   • Lung biopsy (rarely needed) for unclear cases

3. Monitoring:

   • ≥10% ↓FVC or ≥15% ↓DLCO signals significant decline in disease status

Management

IPF

• Antifibrotics: Pirfenidone or nintedanib to slow fibrotic progression

• Pulmonary rehabilitation: Improves functional capacity and QoL

• Long-term oxygen if hypoxaemic; consider lung transplant evaluation in advanced disease

CTD-ILD

• Immunosuppressants: Mycophenolate mofetil, cyclophosphamide (especially in scleroderma-related ILD)

• Treat underlying rheumatologic disease concurrently (e.g. DMARDs for RA, lupus therapy)

Smoking-Related ILD

• Smoking cessation is fundamental

• Corticosteroids if progressive or inflammatory

• Consider lung transplant if advanced

Hypersensitivity Pneumonitis

• Allergen avoidance is critical

• Corticosteroids if severe or progressive disease

Pneumoconioses

• Manage symptoms, avoid ongoing occupational exposures, monitor for progressive fibrotic changes

Special Notes

• HRCT Patterns

  • UIP (usual interstitial pneumonia): Honeycombing, basal/subpleural predominance (classic in IPF, can also appear in RA-ILD)

  • NSIP (nonspecific interstitial pneumonia): More bilateral ground-glass opacities, often linked to CTDs

• Childhood ILD is rare and may require paediatric respiratory referral, genetic testing for familial ILD

Monitoring

• Regular lung function tests (FVC, DLCO) track progression and comorbidities

• Pulmonary rehabilitation improves quality of life and exercise tolerance

• Long-term oxygen therapy if hypoxaemic (PaO₂ <55 mmHg or SpO₂ <88%)

• Refer to specialist (respiratory physician) if uncertain diagnosis, significant disease progression, or complicated comorbidities