Diffuse Fibrosing Alveolitis

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