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Fulminant Pneumonitis: Causes, Features, and Mortality Risk

Definition

Fulminant pneumonitis is a rapidly progressive, severe inflammatory lung injury causing diffuse alveolar damage, profound hypoxemia, and often death within days of onset. It is distinct from typical pneumonia in its speed and severity.

Causes

  • Severe pneumonia: Bacterial (S. pneumoniae, S. aureus, Legionella), viral (influenza, SARS-CoV-2, hantavirus), fungal.
  • Aspiration pneumonitis: Acidic gastric contents (Mendelson's syndrome) → chemical injury + secondary infection.
  • Inhalational injury: Smoke, chlorine, phosgene, nitrogen oxides—direct toxic damage.
  • Drug-induced: Chemotherapy (bleomycin, methotrexate), immunotherapy (checkpoint inhibitors), amiodarone, heroin/cocaine.
  • Immune-mediated: Acute interstitial pneumonitis (AIP/Hamman-Rich), connective tissue disease flare, hypersensitivity pneumonitis.
  • Transfusion-related acute lung injury (TRALI).
  • Near-drowning.

Clinical Presentation

  • Rapid onset (hours to days) of dyspnea, cough, fever.
  • Severe hypoxemia refractory to supplemental O2.
  • Bilateral diffuse infiltrates on CXR/CT (\"white lung\").
  • Non-cardiogenic pulmonary edema (wedge pressure normal).
  • Progression to ARDS criteria (Berlin definition).

Diagnosis

  • Clinical + imaging + exclusion of cardiogenic edema.
  • Bronchoscopy with BAL: rule out infection, hemorrhage, eosinophilia.
  • Serology, PCR, cultures for pathogens.
  • Autoimmune panel if indicated.

Treatment

  • Supportive: Mechanical ventilation (lung-protective strategy), prone positioning, neuromuscular blockade, ECMO for refractory hypoxemia.
  • Etiology-directed: Antimicrobials, antivirals, steroids (for immune-mediated, some drug-induced), stop offending drug.
  • Adjunctive: Conservative fluids, nutrition, DVT/stress ulcer prophylaxis.

Prognosis

Mortality remains high: 40–60% overall, higher in immunocompromised, elderly, or if mechanical ventilation >7 days. Early recognition and ICU-level care improve survival.

Note: COVID-19 causes severe pneumonia/ARDS, but the term \"fulminant pneumonitis\" is more commonly applied to non-infectious or hyperacute infectious processes. The distinction is semantic; management follows ARDS protocols.

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