Idiopathic Pulmonary Fibrosis & Interstitial Lung Disease in PACES

How it presents in PACES

The classic patient is breathless on exertion with a dry, non-productive cough, and on inspection may be tachypnoeic, cyanosed or sitting beside bedside oxygen. The chest expands symmetrically but poorly on both sides, the trachea is central, percussion is resonant and vocal resonance is normal. This combination — reduced expansion with a resonant, quiet chest — should already point you away from consolidation, effusion or a pneumonectomy and towards a diffuse parenchymal process.

A crucial word on terminology, because examiners probe it hard. Interstitial lung disease (ILD), or diffuse parenchymal lung disease, is the umbrella. Pulmonary fibrosis is the end-state. Usual interstitial pneumonia (UIP) is a radiological and histological pattern, and idiopathic pulmonary fibrosis (IPF, the old "cryptogenic fibrosing alveolitis") is simply the idiopathic form of that pattern. The safe move is to name the pattern first and reserve the word "idiopathic" until you have excluded secondary causes.

Signs to look for

The discriminating findings, in the order you should hunt for them:

• Fine, late/end-inspiratory "Velcro" crepitations that do not clear on coughing — this is the clinching sign. Describe the distribution: basal in most, occasionally apical.
• Bilateral, symmetrically reduced chest expansion with a central trachea, resonant percussion and normal vocal resonance.
• Examine the back and bases first — in early disease the only finding may be fine posterior basal crackles that you will miss if you start anteriorly.
• Clubbing (present in roughly half of IPF) — helpful but not discriminating, since it also occurs in bronchiectasis.
• Signs of a connective-tissue cause on the hands and face — sclerodactyly, calcinosis, Raynaud's, telangiectasia, a rheumatoid deforming arthropathy, Gottron's papules or a heliotrope rash.
• Signs of complication: increased work of breathing, central cyanosis, and pulmonary hypertension / cor pulmonale — a raised JVP, a left parasternal heave with a loud or palpable P2, and pedal oedema.

Confirming the diagnosis & differential

The single most useful discriminator at the bedside separates ILD from bronchiectasis, because clubbing appears in both. ILD crackles are fine, Velcro-like, end-inspiratory, numerous (often more than ten per breath) and unchanged by coughing; bronchiectatic crackles are coarse and wet, fewer, and shift or clear with a cough, usually with purulent sputum. The one caveat: advanced fibrosis with traction bronchiectasis can sound coarse, so weigh the whole picture.

Once you have called fibrosis, run the aetiological sieve by zone. Two mnemonics carry most candidates through. Upper-zone fibrosis — SCHART: Silicosis/Sarcoidosis, Coal-worker's pneumoconiosis, Histiocytosis, Ankylosing spondylitis/ABPA, Radiation, TB. Lower-zone fibrosis — RASIO: Rheumatoid arthritis, Asbestosis, Systemic sclerosis, IPF, Others/drugs. Two rules tidy the exceptions: connective-tissue disease gives lower-zone fibrosis except ankylosing spondylitis (upper), and environmental causes give upper-zone disease except asbestosis (lower).

Do not forget the drugs — the "O" of RASIO. Amiodarone (look for slate-grey skin and AF), cytotoxics (bleomycin, methotrexate, cyclophosphamide), antirheumatics (gold, sulfasalazine, leflunomide), nitrofurantoin and phenytoin all cause ILD. Chronic hypersensitivity pneumonitis (bird-fancier's or farmer's lung) is an upper/mid-zone, exposure-driven differential where the history is the diagnostic key.

The viva: what examiners ask

• Investigation of choice — HRCT thorax (thin sections): reticulation, ground-glass, traction bronchiectasis and honeycombing in a basal, peripheral, subpleural distribution; it also separates UIP (honeycombing in ~70%, worst prognosis) from NSIP (younger patients, minimal honeycombing, subpleural sparing, better prognosis).
• Lung function — a restrictive pattern: reduced FVC and TLC, a normal-to-raised FEV1/FVC ratio (>70%), and a reduced transfer factor (DLCO). This is not the obstructive picture of COPD. Track severity with FVC, DLCO and 6-minute-walk desaturation.
• Bloods and serology: a CTD/ENA panel (ANA, RF, anti-CCP, Scl-70, anti-Jo1, dsDNA), plus an ABG which may show type-1 respiratory failure.
• Classification: known-cause DPLD (CTD, occupational, drug); idiopathic interstitial pneumonias (IPF/UIP ~50%, NSIP ~25%, COP, AIP, DIP, RB-ILD); granulomatous (sarcoid); and rarer entities (LAM, Langerhans-cell histiocytosis).
• Complications: pulmonary hypertension complicates 30–40% of ILD and drives mortality — quantify it with an echocardiogram. Also recognise cor pulmonale, respiratory failure, pneumonia and lung carcinoma.
• Management: an ILD-clinic/MDT approach; remove the trigger (stop the offending drug, remove the antigen). For confirmed IPF, antifibrotics (pirfenidone or nintedanib) slow FVC decline, and high-dose steroids are NOT recommended. For CTD-ILD, treat the underlying disease with steroids ± immunosuppression. Add smoking cessation, vaccination, pulmonary rehabilitation, LTOT if hypoxaemic, and consider single-lung transplant in end-stage disease.

Common pitfalls & how to score

• Do not let clubbing decide ILD versus bronchiectasis — the crepitation character does the work.
• Do not credit the fibrosis purely to a connective-tissue disease when the very drugs treating it (methotrexate, leflunomide, sulfasalazine, gold) also cause ILD — the drug and exposure history is part of the standard screen.
• Do not call rheumatoid hands plus crackles "bronchiectasis" reflexively — rheumatoid lung is far more often ILD.
• Reach for "idiopathic" only after exclusion: age over 50, insidious dyspnoea beyond three months, dry cough, a UIP pattern, and no CTD, drug or occupational cause.
• Score marks with the pattern-naming script: "This is a UIP pattern; I would exclude a secondary cause — connective-tissue, drug or occupational — before labelling it idiopathic."