6. Interstitial Lung Disease

📄Definition

ILD is a group of chronic lung disorders causing inflammation and fibrosis of the lung interstitium, leading to progressive breathlessness and impaired gas exchange.

🔬Pathophysiology

🧠 Mnemonic: FIBROSE

  • Fibrosis of alveolar interstitium

  • Inflammatory infiltrate (T-cells, macrophages)

  • Basal and subpleural predominance

  • Restrictive pattern (↓TLC, FVC, DLCO)

  • Over time → honeycombing, traction bronchiectasis

  • Stiff lung = reduced compliance

  • End-stage: pulmonary hypertension + respiratory failure

🛡️Causes of ILD

🧠 Mnemonic: LUNG SCAR

  • Lung disease (TB, pneumonia, COVID pneumonitis)

  • Unknown (Idiopathic Pulmonary Fibrosis – IPF)

  • Neoplasm/radiation

  • Gastro-oesophageal reflux (microaspiration)

  • Sarcoidosis

  • Connective tissue disease (RA, SLE, systemic sclerosis)

  • Asbestos / occupational (coal, silica, hypersensitivity pneumonitis)

  • Reaction to drugs (amiodarone, methotrexate, nitrofurantoin)

📋 Clinical Features

🧠 Mnemonic: DRY AIR

  • Dry cough

  • Restrictive dyspnoea (progressive)

  • Yearning for air (breathless on exertion)

  • Associated clubbing

  • Inspiratory fine crackles (velcro-like)

  • Refractory to treatment (especially IPF)

🩺 Physical Examination Findings

  • Bibasal fine end-inspiratory crackles

  • Finger clubbing

  • Signs of pulmonary hypertension in late disease

  • May have features of connective tissue disorder (joint pain, rash, Raynaud’s)

🔎Investigations

🧠 Mnemonic: BLOOM CT

  • Bloods – ANA, RF, ENA, ANCA (connective tissue screen)

  • Lung function tests (↓FVC, ↓DLCO, normal/↑FEV1:FVC)

  • Oxygen saturation (desaturation on exertion)

  • Open lung biopsy (rare – if diagnosis unclear)

  • Microbiology (rule out infection)

  • CT Chest (HRCT = gold standard: shows honeycombing, reticulation, traction bronchiectasis)

  • Testing for causative agents (occupational exposure, drugs, autoimmune)

Management

🧠 Mnemonic: FIBROSIS PLAN

  • Fibrosis reversal limited – focus on slowing progression

  • Immunosuppressants (e.g. steroids in CTD-related ILD)

  • Breathing support (LTOT if hypoxic)

  • Referral to ILD specialist centre early

  • Oxygen for ambulatory desaturation

  • Symptom relief (opiates for breathlessness, psychological support)

  • Infection prevention: vaccinations

  • Stop causative drug/exposure

  • Pirfenidone or nintedanib for IPF

  • Lung transplant in eligible advanced cases

  • Alveolar rehabilitation

  • Non-invasive ventilation in end-stage

⚠️ Complications

  • Respiratory failure

  • Pulmonary hypertension

  • Cor pulmonale

  • Acute exacerbations

  • Increased risk of lung cancer

  • Depression / reduced QoL

🧐 Differentials

🧠 Mnemonic: CHRONIC

  • COPD (more obstructive)

  • Heart failure (fluid overload crackles)

  • RA-associated bronchiolitis

  • Overweight-related dyspnoea

  • Neoplasm (central obstruction)

  • Infection (esp. post-COVID fibrosis)

  • Connective tissue mimics (sarcoid, vasculitis)

📌 PARA Revision Tips

  • HRCT is gold standard: know typical vs atypical pattern

  • Dry cough + basal crackles + ↓DLCO = think ILD

  • Antifibrotics only approved for IPF

  • Clubbing, crackles, and restrictive spirometry = classic triad

  • Always check occupational and drug history

🔎 Last updated in line with NICE NG163 and BTS/NHS England ILD service specifications
Published: March 2020 • Last updated: May 2023
Last reviewed: July 2025
🔒 PASSMAP ensures all content is NICE-aligned and reviewed for Physician Associate Registration Assessment (PARA) success.

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