Interstitial Lung Disease (ILD) Exacerbation

Acute worsening of ILD — IPF acute exacerbation, CTD-ILD flare, or drug-induced pneumonitis; often rapidly progressive and high mortality

Symptoms / Associated Sx

• Acute or subacute worsening dyspnea over days to weeks

• Dry, non-productive cough

• Hypoxia — often severe; progressive O2 requirement

• Bilateral fine inspiratory crackles ("Velcro" crackles at bases)

• Clubbing (IPF, CTD-ILD — chronic)

• Fever (if infection or drug-induced pneumonitis)

• Constitutional symptoms: weight loss, fatigue, arthralgias (CTD-ILD)

Denies

• Productive purulent cough + fever + consolidation (rules out acute infectious pneumonia as primary if absent — though can trigger AE-IPF)

• New medication exposure within 4–8 weeks (rules out drug-induced pneumonitis — review ALL medications)

• Bilateral edema + elevated BNP (rules out CHF as dominant etiology)

• Chest pain + troponin elevation (rules out ACS-triggered decompensation)

Social History (SHx)

Known ILD diagnosis and type (IPF, NSIP, COP, sarcoidosis, hypersensitivity pneumonitis), prior AE episodes, current pulmonary fibrosis medications (nintedanib, pirfenidone), autoimmune disease (RA, SSc, polymyositis — CTD-ILD), occupational exposures (silica, asbestos, bird droppings — HP), new medications within months (immunosuppressants, amiodarone, nitrofurantoin, bleomycin, immunotherapy).

Main Etiology

• IPF acute exacerbation (AE-IPF): Unknown trigger in ~50%; infection, aspiration, procedure in remaining; bilateral new ground-glass opacities superimposed on honeycomb fibrosis; 50% in-hospital mortality

• CTD-ILD flare: Underlying autoimmune disease (RA, SSc, myositis, SLE, Sjögren) worsening; often responds to immunosuppression

• Drug-induced pneumonitis: Amiodarone, nitrofurantoin, methotrexate, bleomycin, checkpoint inhibitors (anti-PD1/CTLA4), immunotherapy, radiation recall

• Hypersensitivity pneumonitis (HP) flare: Re-exposure to antigen (bird, mold, isocyanate, farmer's lung)

• Superimposed infection triggering ILD worsening

Most Common DDx

• Pneumonia in ILD patient (fever + leukocytosis + consolidation + procalcitonin elevated; treat with antibiotics — can coexist with AE-IPF; bronchoscopy + BAL helps distinguish)

• CHF in ILD patient (elevated BNP; bilateral effusions; cardiomegaly; responds to diuretics; CT shows no new ground-glass without cardiomegaly in AE-IPF)

• Pulmonary embolism (acute onset hypoxia; pleuritic pain; tachycardia; D-dimer + CTPA; ILD patients have increased VTE risk)

• Drug-induced pneumonitis (new drug within 4–8 weeks; eosinophilia on BAL; responds to drug withdrawal + steroids)

• ARDS from non-ILD cause (sepsis, aspiration, trauma — bilateral infiltrates + P/F <300; no prior ILD history)

• Hypersensitivity pneumonitis (antigen exposure history; lymphocytosis on BAL; subacute upper lobe predominant GGO; antigen avoidance critical)

DATA

• CBC (leukocytosis → infection; eosinophilia → drug-induced/HP)

• BMP, BNP (cardiac contribution)

• LFTs (drug-induced liver + lung toxicity — amiodarone, methotrexate)

• Procalcitonin (infection vs. sterile AE)

• Blood cultures × 2; respiratory viral panel; Legionella/pneumococcal urine antigens

• CT chest HRCT (high-resolution CT — gold standard; AE-IPF: new GGO + consolidation superimposed on pre-existing honeycomb; UIP pattern)

• Echocardiogram (pulmonary hypertension, RV function, cardiac contribution)

• Bronchoscopy + BAL (cell differential — neutrophilia: AE-IPF; lymphocytosis: HP, drug; eosinophilia: drug/eosinophilic; cultures to exclude infection)

• ABG (PaO2, P/F ratio, A-a gradient)

• Autoimmune panel: ANA, anti-dsDNA, RF, anti-CCP, anti-Jo-1, anti-Scl70, anti-MDA5 (CTD-ILD)

• Pulmonary function tests (FVC % predicted — severity; deferred during acute)

Home Meds

• Nintedanib (Ofev) or pirfenidone (Esbriet) — antifibrotic agents for IPF; continue during exacerbation

• Immunosuppressants for CTD-ILD (mycophenolate, azathioprine, rituximab — continue or escalate)

• Checkpoint inhibitors (pembrolizumab, nivolumab — hold immediately if immune checkpoint inhibitor pneumonitis)

• Amiodarone, nitrofurantoin, methotrexate — identify and stop if drug-induced

• Home O2 (flow rate; assess adequacy)

Plan

• Supplemental O2 — target SpO2 ≥92%; escalate to HFNC if inadequate; early NIV discussion; intubation decision is particularly complex in IPF (see below)

• Exclude infection (blood cultures, respiratory viral panel, bronchoscopy + BAL cultures) before or concurrent with steroids

• Empiric antibiotics (while excluding infection): Piperacillin-tazobactam 3.375 g IV q6h OR Ceftriaxone 2 g IV daily + Azithromycin 500 mg IV daily; narrow or stop based on culture results and BAL

• AE-IPF — corticosteroids (empiric; limited evidence but standard practice):

  • Methylprednisolone 0.5–1 g IV daily × 3 days ("pulse steroids") → prednisone 1 mg/kg/day PO × 4 weeks → taper over 3–6 months

  • Evidence is limited; some patients respond transiently; ~50% in-hospital mortality despite treatment

• Drug-induced pneumonitis:

  • Stop offending agent IMMEDIATELY

  • Prednisone 1–2 mg/kg/day PO (or methylprednisolone 1–2 mg/kg IV) × 4–8 weeks → slow taper

  • Checkpoint inhibitor pneumonitis (Grade 2–3): Hold immunotherapy + prednisone 1–2 mg/kg/day; Grade 4 → add cyclophosphamide or infliximab if steroid-refractory; oncology consult

• CTD-ILD flare:

  • High-dose steroids + escalate immunosuppression (mycophenolate, rituximab per underlying CTD)

  • Rheumatology consult

• Hypersensitivity pneumonitis: Remove antigen exposure; prednisone 0.5 mg/kg/day; chronic HP → antigen avoidance is curative in early disease

• Intubation decision in AE-IPF:

  • Controversial — median survival after intubation in AE-IPF is <1 month; ICU mortality >90%

  • Discuss goals of care and palliative care early; lung transplant evaluation if eligible

  • HFNC or CPAP as a trial before intubation discussion

• Continue antifibrotic therapy (nintedanib/pirfenidone) — evidence for benefit in AE-IPF

• Pulmonology consult + ILD specialist; palliative care consultation early in IPF exacerbation

• Lung transplant referral if AE-IPF and candidate (<65, no contraindications)

• Daily ABG, SpO2, CBC, BMP, CRP; trend O2 requirement

• PT/OT — pulmonary rehab; energy conservation techniques

• Discharge: Continue steroids with taper plan; antifibrotic agents (IPF); immunosuppression (CTD-ILD); home O2 if needed; pulmonology follow-up 1–2 weeks; repeat CT chest at 6–8 weeks; lung transplant referral for eligible patients; advance directives discussion

Red Flags

• P/F <200 in AE-IPF → ICU; early goals-of-care discussion; palliative care; lung transplant evaluation if candidate

• Rapidly progressive hypoxia (>3L O2 increase in 24h in ILD patient) → impending respiratory failure → HFNC or CPAP trial; ICU

• Checkpoint inhibitor pneumonitis (Grade 3–4 — SpO2 <88% or new O2 requirement) → hold immunotherapy permanently; high-dose steroids; oncology + pulmonology

• AE-IPF without identifiable trigger → highest mortality; early goals-of-care conversation; intubation rarely beneficial

• Amiodarone pneumonitis (bilateral infiltrates + elevated LFTs + amiodarone use) → stop amiodarone immediately; taper steroids × months; slow resolution

Senior IM Resident Pearls

• AE-IPF in-hospital mortality is ~50% — early palliative care and goals-of-care conversation is NOT giving up; it is good medicine; discuss intubation limitations honestly with patients and families

• UIP pattern on HRCT (honeycombing + basal subpleural reticulation ± traction bronchiectasis) = IPF until proven otherwise; no biopsy needed if HRCT is classic UIP + no alternative diagnosis

• Checkpoint inhibitor pneumonitis can occur weeks to months after starting treatment — any new pulmonary infiltrates in patient on anti-PD1/PD-L1/CTLA4 therapy → hold drug and treat with steroids; re-challenge depends on severity and oncology judgment

• BAL cell differential is crucial in ILD exacerbation: neutrophils = AE-IPF or infection; lymphocytes = HP or drug-induced or CTD; eosinophils = drug-induced or AEP; helps guide immunosuppression vs. antibiotics

• Common mistake: Starting high-dose steroids in AE-IPF without BAL or at least blood cultures — if infection is the trigger, steroids worsen outcome; minimize antibiotics and steroids together empirically; bronchoscopy is essential