Last reviewed 01/2018

Allergic extrinsic alveolitis is a hypersensitivity reaction affecting the lung parenchyma occurring in response to inhaled inorganic dusts.

The pathogenesis is thought to be different in acute and chronic cases:

  • acute:
    • usually the result of a type III - immune complex - hypersensitivity reaction
    • precipitins can be demonstrated in the serum

  • chronic:
    • principally a type IV (cell-mediated) hypersensitivity reaction, characterised by:
      • lymphocyte infiltration
      • giant cells
      • granulomata
      • diffuse lung fibrosis
      • endobronchial exudates
      • bronchiolitis obliterans