Interstitial lung disease

Progressive dyspnea, dry cough, velcro crackles, clubbing, restriction + low DLCO. History: CTD, drugs, birds/mold, radiation, smoking.

Sophie Nick5 min6 questions4 trials

Frame

ILD replaces normal lung with inflammation and/or fibrosis (). Patients arrive with progressive dyspnea, dry cough, and exertional hypoxemia. Velcro crackles, clubbing, and a rheumatologic extra are the exam.

Three pattern families

Interstitial
UIP, NSIP, bronchiolocentric (BIP), PPFE, LIP.
Alveolar filling
DAD, organizing pneumonia, RB-ILD, alveolar macrophage pneumonia, PAP, eosinophilic pneumonia.
Combined / unclassifiable
NSIP+OP, UIP+PPFE, or more than one undefined pattern.

Each pattern has an idiopathic form and secondary causes (CTD, HP, drugs, radiation, occupational).

HRCT pattern	Look	Think
UIP	Heterogeneous, subpleural/basal, honeycombing, traction bronchiectasis	IPF, CTD, HP, drugs. 91% sensitive, 71% specific for the clinical diagnosis ().
NSIP	Lower-lobe reticulation/GGO, more homogeneous, micronodules	CTD, HP, drugs — often more steroid-responsive than UIP
OP	Patchy peripheral/perilobular consolidation with subpleural sparing	Post-infectious, CTD, drugs, aspiration
HP / BIP clues	Mosaic, air trapping, upper/mid-zone peribronchovascular fibrosis	Birds, molds, hot tubs, humidifiers
LIP	Centrilobular GGO, cysts, septal thickening	Sjögren, immunodeficiency

Workup and treatment

Multidisciplinary discussion is the diagnostic gold standard — not a lone biopsy.
Remove exposures first. If they improve, you are done.
Labs: CBC, CMP, C3/C4, CK/aldolase, myositis and HP panels, ANA, RF/CCP, RNP, Ro/La, Scl-70, ANCA, GBM. HIV and hepatitis when infection is on the table.
Do not biopsy definite UIP — morbidity and exacerbation risk (). Cryobiopsy is less invasive than VATS if the pattern is truly unclear.
Severity: 6MWT and PFTs. Restriction (↓ TLC, FRC, RV) with a preserved or high FEV1/FVC. ↓ DLCO can be the earliest change.

Disease-modifying therapy

IPF: nintedanib (, ), pirfenidone (, ), nerandomilast (). They slow FVC decline; they are not a cure. Treat GERD for reflux symptoms, not “for the lung” (ATS 2022).
IPF exacerbation: steroids ~1 mg/kg plus broad antibiotics (vanc / cefepime / azithro) for 7 days while you rule out PE, HF, and infection.
SSc-ILD: nintedanib (), MMF, cyclophosphamide, rituximab, tocilizumab.
Idiopathic NSIP: prednisone 0.5–1 mg/kg (or pulse if hospitalized) ± AZA, MMF, rituximab, cyclophosphamide.