AKT · Respiratory/ILD, sarcoid & occupational

Interstitial lung disease & pulmonary fibrosis

Diffuse parenchymal lung disease → inflammation/fibrosis of the interstitium (restrictive, low DLCO)

Overview

A group of diffuse parenchymal lung diseases causing inflammation and/or fibrosis of the interstitium, with a RESTRICTIVE pattern and reduced gas transfer (DLCO). Idiopathic pulmonary fibrosis (IPF) is the commonest progressive form (basal/peripheral honeycombing, antifibrotics); others are drug-induced, connective-tissue-disease-associated, hypersensitivity pneumonitis, sarcoidosis and pneumoconioses. Progressive exertional breathlessness with fine crackles and clubbing is the picture.

Recognise

Progressive exertional breathlessness, dry cough, fine bibasal 'velcro' inspiratory crackles, finger clubbing (IPF)
Spirometry: RESTRICTIVE (FEV1/FVC normal/high, reduced FVC) with reduced gas transfer (DLCO); HRCT — reticulation, traction bronchiectasis, basal/subpleural HONEYCOMBING (UIP pattern in IPF)
Causes: idiopathic (IPF), drugs (amiodarone, methotrexate, nitrofurantoin, bleomycin), connective tissue disease, hypersensitivity pneumonitis, sarcoidosis, asbestosis

Red flags

Acute exacerbation of IPF (rapid deterioration) → high mortality, specialist care
A new ILD on a drug (amiodarone/methotrexate/nitrofurantoin) → stop the culprit drug

Differentials & how to tell them apart

Heart failureraised JVP/BNP, responds to diuretics; bibasal crackles but no honeycombing

COPD/emphysemaobstructive, not restrictive; different HRCT

Drug-/CTD-/exposure-related ILDidentifiable cause — stop the drug/treat the CTD/remove the antigen

Usual interstitial pneumonia — peripheral/basal honeycombing on HRCT
Yale Rosen / CC BY-SA 2.0 — Wikimedia Commons

Investigations

Spirometry (restrictive) + DLCO (reduced); HRCT chest (pattern — UIP/honeycombing in IPF); autoimmune screen (connective-tissue disease), drug and occupational/exposure history; sometimes lung biopsy/bronchoalveolar lavage; MDT diagnosis.

Management

Treat/remove the cause; IPF → antifibrotics (pirfenidone/nintedanib); inflammatory ILD → immunosuppression

1Recognise a restrictive pattern with reduced DLCO and confirm with HRCT (UIP/honeycombing in IPF); take a careful drug, occupational and autoimmune history (MDT diagnosis).Gate: IPF does NOT respond to steroids (and immunosuppression may harm) → use antifibrotics; inflammatory/CTD-related ILD DOES respond to immunosuppression — distinguish them. Stop a culprit drug (amiodarone/methotrexate/nitrofurantoin).
2Treat the underlying cause; antifibrotics for IPF, immunosuppression for inflammatory ILD; supportive oxygen/rehab/vaccines; consider transplant in selected patients.

Remove the cause + treat the underlying disease — stop the culprit drug, treat connective-tissue disease, remove the antigen (hypersensitivity pneumonitis)

IPF: antifibrotics (pirfenidone or nintedanib) — slow decline in IPF; steroids/immunosuppression do NOT help IPF (and may harm) but DO help inflammatory ILDs

Immunosuppression for inflammatory/CTD-ILD — corticosteroids ± steroid-sparing agents where there is an inflammatory component

Supportive: oxygen, pulmonary rehab, vaccines; lung transplant for selected patients — palliative symptom control as needed

Key points

Progressive breathlessness + dry cough + fine 'velcro' basal crackles + clubbing + RESTRICTIVE spirometry/low DLCO + HRCT honeycombing = pulmonary fibrosis. IPF → ANTIFIBROTICS (pirfenidone/nintedanib); steroids don't help IPF (may harm) but DO help inflammatory/CTD-ILD. Always check drugs (amiodarone/methotrexate/nitrofurantoin/bleomycin).

Monitor & prognosis

FVC/DLCO trajectory, oxygenation, exacerbations; drug/CTD activity.

IPF progressive with poor prognosis (antifibrotics slow it); inflammatory ILDs better with treatment.

Source: NICE CG163 (IPF); ILD MDT