What is interstitial lung disease?

ILDs are a heterogeneous group of >200 diffuse parenchymal lung conditions characterised by inflammation or fibrosis of the lung interstitium, alveolar walls and surrounding structures. Most clinically important: IPF (most common IIP; worst prognosis); HP (most common treatable ILD); CTD-ILD (RA, SSc, myositis, Sjögren's); NSIP; sarcoidosis stage III-IV; drug-induced ILD. ILDs share: progressive exertional breathlessness; dry cough; bibasilar crackles on auscultation; restrictive spirometry + reduced DLCO.

What is IPF and how is it treated?

IPF is a chronic, progressive fibrosing ILD of unknown cause — predominantly affecting adults >60 years, predominantly men, predominantly smokers/ex-smokers. UIP pattern on HRCT. Median survival 3-5 years. Two antifibrotic drugs (FDA 2014): nintedanib (Ofev — TKI); pirfenidone (Esbriet — TGF-β inhibitor). Both reduce FVC decline ~50% and reduce AE-IPF. Neither reverses fibrosis or dramatically extends survival. Additional: supplemental oxygen (SpO2 <88% on 6MWT); pulmonary rehabilitation; manage GORD; lung transplant (for eligible patients); advance care planning.

What is hypersensitivity pneumonitis?

HP is a treatable immune-mediated ILD from repeated organic antigen inhalation. Common causes: bird-fancier's lung (feathers, droppings); farmer's lung (mouldy hay — thermophilic bacteria); hot tubs; home humidifiers; occupational (isocyanates, wood dust). Key: HP can stabilise or improve with ANTIGEN AVOIDANCE — particularly in acute/subacute phase. Chronic HP can develop fibrotic UIP-like pattern mimicking IPF — making antigen history essential. HRCT: upper lobe or diffuse GGO + centrolobular nodules + mosaic air trapping (not lower lobe honeycombing).

What are the CTD-associated ILDs?

CTD-ILD occurs in: SSc (~80% have some ILD; NSIP most common; nintedanib proven in SENSCIS trial); RA-ILD (UIP most common — worse prognosis than NSIP; methotrexate can worsen — careful monitoring); inflammatory myopathy (anti-synthetase syndrome ILD; anti-MDA5 RP-ILD — see inflammatory myopathy hub); Sjögren's (LIP most specific; NSIP also); SLE (ILD less common; acute lupus pneumonitis). Screen all CTD patients with PFTs + HRCT if symptomatic or PFTs abnormal.

How does GMJ News cover ILD?

GMJ News covers IPF (prognosis, UIP pattern, nintedanib/pirfenidone), HP (most common treatable ILD — antigen avoidance), CTD-ILD, HRCT patterns (UIP vs NSIP vs HP), BAL cell differentials, AE-IPF (50-80% mortality), familial IPF telomere genetics, 6MWT oxygen threshold, and lung transplant criteria.

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Interstitial Lung Disease

Q: What is hypersensitivity pneumonitis?

HP is a treatable immune-mediated ILD from repeated organic antigen inhalation. Common causes: bird-fancier's lung (feathers, droppings); farmer's lung (mouldy hay — thermophilic bacteria); hot tubs; home humidifiers; occupational (isocyanates, wood dust). Key: HP can stabilise or improve with ANTIGEN AVOIDANCE — particularly in acute/subacute phase. Chronic HP can develop fibrotic UIP-like pattern mimicking IPF — making antigen history essential. HRCT: upper lobe or diffuse GGO + centrolobular nodules + mosaic air trapping (not lower lobe honeycombing).

Q: What are the CTD-associated ILDs?

CTD-ILD occurs in: SSc (~80% have some ILD; NSIP most common; nintedanib proven in SENSCIS trial); RA-ILD (UIP most common — worse prognosis than NSIP; methotrexate can worsen — careful monitoring); inflammatory myopathy (anti-synthetase syndrome ILD; anti-MDA5 RP-ILD — see inflammatory myopathy hub); Sjögren's (LIP most specific; NSIP also); SLE (ILD less common; acute lupus pneumonitis). Screen all CTD patients with PFTs + HRCT if symptomatic or PFTs abnormal.

Q: How does GMJ News cover ILD?

GMJ News covers IPF (prognosis, UIP pattern, nintedanib/pirfenidone), HP (most common treatable ILD — antigen avoidance), CTD-ILD, HRCT patterns (UIP vs NSIP vs HP), BAL cell differentials, AE-IPF (50-80% mortality), familial IPF telomere genetics, 6MWT oxygen threshold, and lung transplant criteria.

GMJ News knowledge hub · last reviewed August 2026 · Georgian Medical Journal

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Interstitial lung diseases (ILDs) — a heterogeneous group of parenchymal lung conditions characterised by diffuse alveolar damage, fibrosis or inflammation — encompass over 200 distinct entities, of which idiopathic pulmonary fibrosis (IPF) is the most common and most feared: with a median survival of approximately 3-5 years from diagnosis and no curative treatment, driven by progressive, irreversible fibrosis in a characteristic UIP (usual interstitial pneumonia) pattern on HRCT and pathology that does not respond to immunosuppression (WHO/ERS). Two antifibrotic drugs have transformed IPF management: nintedanib (Ofev, FDA 2014) — a tyrosine kinase inhibitor (VEGFR, FGFR, PDGFR) — and pirfenidone (Esbriet, FDA 2014) — a TGF-β inhibitor — both reduce the rate of FVC decline by approximately 50% and reduce acute exacerbations, though neither reverses fibrosis or significantly extends survival; while hypersensitivity pneumonitis (HP) — the most common treatable ILD — requires identification and removal of the antigen (feathers, mould, bird proteins, occupational exposures).

Key messages

IPF — median survival 3-5 years; nintedanib and pirfenidone slow progression

Idiopathic pulmonary fibrosis (IPF): the most common IIP (idiopathic interstitial pneumonia) and the most feared — progressive, irreversible UIP-pattern fibrosis with median survival ~3-5 years from diagnosis. Two antifibrotic agents (both FDA 2014): nintedanib (Ofev — TKI blocking VEGFR, FGFR, PDGFR); pirfenidone (Esbriet — TGF-β pathway inhibitor). Both reduce annual FVC decline by ~50% and reduce acute exacerbation frequency. Neither reverses fibrosis or meaningfully extends survival.

UIP pattern on HRCT — the diagnostic hallmark of IPF

Typical UIP (pathognomonic for IPF in appropriate clinical context): peripheral, subpleural, bibasilar predominance; honeycombing (stacked cysts — most specific finding); traction bronchiectasis. Absence of: ground glass opacity predominance; upper lobe predominance; peribronchovascular predominance (all suggest NSIP, HP, or DIP instead). HRCT is the cornerstone of ILD diagnosis — surgical lung biopsy reserved for diagnostically uncertain cases.

Hypersensitivity pneumonitis — the most common treatable ILD

HP (extrinsic allergic alveolitis): immune-mediated lung inflammation from repeated organic antigen inhalation — most commonly bird feathers/droppings (bird-fancier's lung); mould/thermophilic bacteria (farmer's lung, hot tub lung); occupational antigens (isocyanates, wood dust). Key difference from IPF: HP can stabilise or improve with ANTIGEN AVOIDANCE. Chronic HP can mimic IPF — antigen history is the critical differentiator.

BAL cell differentials — distinguishing ILD subtypes

BAL lymphocytosis (>20-30%): HP (often very high >40%); NSIP; sarcoidosis; DIP. Neutrophilia: IPF (rarely high lymphocytes); drug-induced ILD; acute IP. Eosinophilia: eosinophilic pneumonia; drug-induced ILD. CD4:CD8 ratio >3.5: sarcoidosis. Note: BAL not always required — HRCT + clinical context often sufficient for IPF diagnosis; BAL most useful when diagnosis is uncertain.

Acute exacerbation of IPF — 50-80% in-hospital mortality

AE-IPF: rapid unexplained worsening of breathlessness over <1 month with new bilateral GGO on HRCT superimposed on UIP background — no identifiable cause (infection, HF, PE, PTX). Mortality: 50-80% in-hospital. No proven treatment — high-dose corticosteroids universally used despite poor evidence; continue antifibrotics; palliative/supportive care. Arrange advance care planning early in all IPF patients.

CTD-ILD — screen all connective tissue disease patients

CTD-associated ILD occurs in: SSc (~80% have some ILD; NSIP most common; nintedanib proven-SENSCIS); RA-ILD (UIP most common; NSIP also; methotrexate can worsen); inflammatory myopathy (anti-synthetase ILD; anti-MDA5 RP-ILD); Sjögren's (LIP most specific; NSIP also). Screen ALL CTD patients with PFTs (FVC + DLCO) + HRCT if symptomatic or PFTs abnormal.

Key statistics

3-5 years

median survival for IPF from diagnosis

ATS/ERS/JRS/ALAT

~50%

reduction in annual FVC decline with nintedanib or pirfenidone (INPULSIS/CAPACITY)

NEJM 2014

FDA 2014

both nintedanib (Ofev) and pirfenidone (Esbriet) approved for IPF in October 2014

FDA 2014

UIP

honeycombing + peripheral subpleural bibasilar pattern = pathognomonic for IPF on HRCT

ATS/ERS 2022

most common treatable ILD — antigen avoidance is the most important intervention

ATS/ERS

50-80%

in-hospital mortality from acute exacerbation of IPF

ATS/ERS/JRS/ALAT

ILD subtypes — frequency and key clinical features (ATS/ERS)

Source: ATS/ERS. IPF most common IIP; HP most common treatable ILD; CTD-ILD important reversible cause.

Glossary of key terms

UIP vs NSIP vs HP on HRCT
Radiology/RespiratoryUIP (IPF): subpleural bibasilar honeycombing + traction bronchiectasis; minimal GGO; no upper lobe predominance. NSIP (CTD-ILD, idiopathic): bilateral symmetrical GGO > fibrosis; subpleural sparing; lower lobe; honeycombing rare/absent; better prognosis than IPF. HP: upper lobe or diffuse GGO; centrolobular nodules; mosaic air trapping (expiratory); no/minimal honeycombing in acute/subacute; can progress to UIP-like in chronic HP.

Nintedanib (Ofev)
FDA 2014/Boehringer IngelheimIntracellular TKI blocking VEGFR, FGFR, PDGFR — growth factor signalling driving fibroblast proliferation/differentiation in IPF. INPULSIS trials (NEJM 2014): 50% reduction in annual FVC decline (125 vs 240 mL/year). Side effects: diarrhoea (~60% — manageable with loperamide/dose reduction); elevated LFTs (monitor); thromboembolism; teratogenic. Also approved for SSc-ILD (SENSCIS) and progressive fibrosing ILDs other than IPF (INBUILD).

Pirfenidone (Esbriet)
FDA 2014/RocheSynthetic molecule with antifibrotic, anti-inflammatory and antioxidant properties — inhibits TGF-β1-stimulated collagen synthesis and fibroblast proliferation. ASCEND trial (NEJM 2014): significant FVC decline reduction + reduced mortality. Side effects: nausea (~36%); photosensitivity (mandatory sunscreen; avoid sun exposure); rash; dizziness. Dose: 2,403mg/day in 3 divided doses with food.

6MWT and oxygen supplementation in ILD
Pulmonary function6-minute walk test (6MWT): patient walks flat surface for 6 minutes. 6MWT distance (6MWD) normal >400m. SpO2 <88% during 6MWT = indication for ambulatory supplemental oxygen. In ILD: 6MWD correlates with disease severity, QoL and mortality. Decrease >50m from baseline = clinically meaningful decline. Oxygen supplementation for patients desaturating <88% on 6MWT: improves exercise capacity and QoL.

Familial IPF — telomere genetics
Genetics/PulmonologyTERT and TERC mutations → short telomeres → impaired alveolar epithelial repair → progressive fibrosis. Familial IPF (~5-10% of all IPF): ≥2 family members with IIP. Features: younger onset; associated hepatic nodular regenerative hyperplasia; aplastic anaemia/MDS (short marrow telomeres); nail dysplasia; oral leukoplakia (dyskeratosis congenita spectrum). Cascade testing; leukocyte telomere length by flow-FISH; lung transplant (may develop BOS more rapidly).

Lung transplantation criteria in ILD
Transplant/PulmonologyLung transplant is the only curative option for IPF — limited by donor availability, age (<65-70), fitness and post-transplant complications. ATS/ERS IPF referral criteria: DLCO <40% predicted; FVC decline ≥10% in 6 months; DLCO decline ≥15% in 6 months; SpO2 <88% on 6MWT; honeycombing on HRCT. Refer EARLY — waiting list times 1-3 years. CTD-ILD with progressive decline: also refer (generally better transplant prognosis than IPF).

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Interstitial Lung Disease

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