Diffuse Fibrosing Alveolitis

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Diffuse Fibrosing Alveolitis/ Interstitial Pneumonia

  • Diffuse inflammatory process which occurs distal to the terminal bronchioles
  • Characterised by thickening and fibrosis of the alveolar walls
  • The precise underlying aetiology of this condition is obscure and it is likely to represent the end stage of a variety of initial insults including EAA and fog fever
  • Progression from an acute exudative phase through a proliferative phase (proliferation of type II pneumocytes) to a final irreversible stage of fibrosis is the hallmark of DFA
  • The rate of the ensuing fibrosis is heavily dependant on the intensity of the inflammation associated with it
  • Underlying pathogenesis of the fibrosis is complex and involves a relative increase of type I collagen fibres (dense, high tensile strength) over type III fibres (reticulin)
  • Stimulation of fibroblast proliferation and collagen deposition are thought to be induced by macrophage derived cytokines, e.g. IL-1, TGFalpha and TGFbeta, GM-CSF
Diffuse fibrosing alveolitis (Image sourced from Bristol Biomed Image Archive with permission)
  • Chronic disease of adult cattle occuring sporadically
  • Probably caused by repeated subclinical incidents of fog fever or farmer's lung
  • Farmer's Lung
    • Extrinsic allergic alveolitis
    • Hypersensitivity of ingested or inhaled moulds
    • May occur as an outbreak or sporadically in adult cattle
  • Hypersensitivity diseases often cause an lymphocytic interstitial pneumonia
  • Chronic interstitial pneumonia progresses to fibrosis
    • Sometimes called pneumonitis