21-HYPERSENSITIVITY PNEUMONITIS

• Extrinsic allergic alveolitis


  Previously known as
• Exaggerated immunological response to an antigen

  • Ex: Farmer's lung (moldy hay actinomyces)
  • Bird fancier's lung (pigeons/bird droppings)
  • Fungi
• Widespread inflammation

  In alveoli & bronchioles from organic dust inhalation
• Presentation

  1. Hours after exposure: fever, malaise, SOB, cough, tachypnea, course inspiratory crackles, inspiratory squeaks

  2. Symptoms markedly decreases after last exposure

  3. Continuing exposure: chronic illness - insidious onset of respiratory (dyspnea) & constitutional (weight loss) symptoms +/- clubbing, may lead to irreversible fibrosis
• IgG antibodies against Ag are the evidence of exposure
• Labs show neutrophilia and eosinophilia
• CXR: fluffy nodular shadowing esp. in upper zones
• HRCT: reticular & nodular pattern with ground glass appearance
• Bronchoalveolar lavage: high killer T-cells CD8
• Treatment

  1. Avoiding allergens

  2. Corticosteroids to reduce inflammation (if symptoms are severe and persistent)