Extrinsic allergic alveolitis

Extrinsic allergic alveolitis

Extrinsic allergic alveolitis (EAA, also known as hypersensitivity pneumonitis) is a condition caused by hypersensitivity induced lung damage due to a variety of inhaled organic particles. It is thought to be largely caused by immune-complex mediated tissue damage (type III hypersensitivity) although delayed hypersensitivity (type IV) is also thought to play a role in EAA, especially in the chronic phase.

Examples

• bird fanciers' lung: avian proteins from bird droppings
  avian proteins from bird droppings
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• farmers lung: spores of Saccharopolyspora rectivirgula
  Saccharopolyspora rectivirgula causes farmer's lung, a type of EAA
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  Importance: 67
  from wet hay (formerly Micropolyspora faeni)
• malt workers' lung: Aspergillus clavatus
  Aspergillus clavatus causes malt workers' lung, a type of EAA
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  Importance: 68
• mushroom workers' lung: thermophilic actinomycetes*

Presentation

• acute (occurs 4-8 hrs after exposure)
  • dyspnoea
  • dry cough
  • fever
• chronic (occurs weeks-months after exposure)
  • lethargy
  • dyspnoea
  • productive cough
  • anorexia and weight loss

Investigation

• imaging: upper/mid-zone fibrosis
  Extrinsic allergic alveolitis is associated with upper/mid zone lung fibrosis
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  Importance: 58
• bronchoalveolar lavage: lymphocytosis
• serologic assays for specific IgG antibodies
• blood: NO eosinophilia

Management

• avoid precipitating factors
  avoid precipitating factors
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• oral glucocorticoids

*here the terminology is slightly confusing as thermophilic actinomycetes is an umbrella term covering strains such as Micropolyspora faeni

+PassMedicine Notes

Extrinsic allergic alveolitis (EAA, also known as hypersensitivity pneumonitis) is a condition caused by hypersensitivity induced lung damage due to a variety of inhaled organic particles. It is thought to be largely caused by immune-complex mediated tissue damage (type III hypersensitivity) although delayed hypersensitivity (type IV) is also thought to play a role in EAA, especially in the chronic phase.

Examples

• bird fanciers' lung: avian proteins from bird droppings
• farmers lung: spores of Saccharopolyspora rectivirgula from wet hay (formerly Micropolyspora faeni)
• malt workers' lung: Aspergillus clavatus
• mushroom workers' lung: thermophilic actinomycetes*

Presentation

• acute (occurs 4-8 hrs after exposure)
• dyspnoea
• dry cough
• fever
• chronic (occurs weeks-months after exposure)
• lethargy
• dyspnoea
• productive cough
• anorexia and weight loss

Investigation

• imaging: upper/mid-zone fibrosis
• bronchoalveolar lavage: lymphocytosis
• serologic assays for specific IgG antibodies
• blood: NO eosinophilia

Management

• avoid precipitating factors
• oral glucocorticoids

*here the terminology is slightly confusing as thermophilic actinomycetes is an umbrella term covering strains such as Micropolyspora faeni

xrb206.jpg xrb207.jpg Chest x-ray and CT scan from a middle-aged woman who presented with dyspnoea. The CT demonstrates multuple centrilobular ground glass nodules consistent with hypersensitivity pneumonitis