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Mechanistic Deep Dive
IPF Pathogenesis
- Repetitive epithelial injury (smoking, GERD, environmental)
- Aberrant wound healing
- Fibroblast proliferation
- Collagen + ECM deposition
- Genetic susceptibility: MUC5B promoter, TERT, SFTPC, MUC2
UIP Pattern Histology
- Spatial + temporal heterogeneity
- Fibroblast foci
- Honeycombing
- Architectural distortion
- Subpleural / paraseptal predominance
Antifibrotic Mechanism
- Pirfenidone: anti-TGF-β + anti-inflammatory + antioxidant
- Nintedanib: tyrosine kinase inhibitor (PDGF, FGF, VEGF)
- Both slow FVC decline ~ 50%
Recent Trials & Updates
INBUILD (2019) â Nintedanib for Progressive Pulmonary Fibrosis
- N = 663 non-IPF progressive fibrotic ILD
- Nintedanib slowed FVC decline
- Established treatment for PPF any cause
- 2020 FDA approval for PPF
SENSCIS (2019) â Scleroderma-ILD
- Nintedanib for SSc-ILD
- Slowed FVC decline
- Often combined with MMF
- 2020 FDA approval for SSc-ILD
Anti-MDA5 + Rapidly Progressive ILD
- Severe phenotype
- Treatment: aggressive immunosuppression (cyclophosphamide + rituximab + tofacitinib + plasmapheresis)
- High mortality
TRAIL1 (2024) â Pamrevlumab
- Anti-CTGF antibody
- Phase 3 for IPF
- Mixed results; not approved
INMARK + INSTAGE â Nintedanib in Early IPF / Combination
- Combination strategies
- Earlier treatment
Sirolimus in LAM (MILES, 2011 + follow-up)
- Stabilizes FEV1 decline
- Continued use needed
- Approved for LAM
High-Yield Specialist Points
MUC5B Polymorphism in IPF
- rs35705950
- 30% of population carrier
- Most common genetic risk factor
- Associated with longer survival paradoxically
Cryobiopsy vs Surgical Biopsy
- Cryobiopsy: 80%+ diagnostic yield, â mortality
- Surgical: gold standard, â tissue volume, â morbidity
- MDD often integrates without biopsy
Antifibrotic in Combination
- Combination not standard
- Trials testing
- Single-agent at maximum dose preferred
GERD + IPF
- Common comorbidity
- Microaspiration may worsen
- PPI / fundoplication
- 2024 ATS guidelines mixed evidence
Pulmonary Hypertension + ILD
- Common (Group 3 PH)
- Worsens outcomes
- INCREASE trial: inhaled treprostinil
- Specialty referral
Acute Exacerbation IPF
- < 30 days new dyspnea
- New ground-glass on HRCT
- Exclude infection, HF, PE
- Treatment: high-dose steroids (debated), supportive
- 50%+ 30-day mortality
Lung Transplant Referral Timing
- FVC < 50% predicted OR
- DLCO < 35% predicted OR
- Hospitalization for exacerbation OR
- Progressive decline despite antifibrotic
- Earlier referral important (organ wait times)
Anti-Synthetase Syndrome
- Anti-Jo-1, PL-7, PL-12 antibodies
- ILD + mechanicâs hands + arthritis + Raynaud + fever
- Often presents with ILD
- Aggressive IS
Vasculitis + Pulmonary Hemorrhage
- Goodpasture (anti-GBM)
- ANCA-associated (GPA, MPA)
- Plasmapheresis + steroids + cyclophosphamide / rituximab
Drug-Induced ILD Severity
- Amiodarone: usually requires high-dose + months
- ICI: spectrum mild â severe (Class IIa)
- Methotrexate: hypersensitivity pattern
- ICI rechallenge: limited data; case-by-case
Pearls
- ILD: 200+ disorders; classified by 2013 ATS/ERS framework
- IPF: UIP pattern, worst prognosis; antifibrotic standard
- INBUILD: nintedanib for progressive pulmonary fibrosis any cause
- NSIP: better prognosis, CTD-associated, immunosuppressive
- COP: migratory consolidation, dramatic steroid response
- Sarcoidosis: non-caseating granulomas, BAL CD4/CD8 > 4
- MDD: gold standard for ILD diagnosis
- LAM: women + TSC association + sirolimus
- PAP: anti-GM-CSF + crazy paving + whole lung lavage
- Lung transplant: for end-stage; early referral