Pulmonary fibrosis.

Diffuse interstitial pulmonary fibrosis is the end result of alveolar damage which may occur as a sudden acute incident or as a slowly developing process. Potentiating factors include release of enzymes and generation of oxygen radicals by granulocytes. Evidence from studies on broncho-alveolar lavage fluid and from immunocytochemistry indicate that an autoimmune process has an important but, as yet, not clearly defined role in initiating the disease. The fibrosis is probably due to proliferation of small clones of fast growing fibroblasts of a specific phenotype. Bronchiolitis obliterans, organizing pneumonia, idiopathic pulmonary fibrosis, usual interstitial pneumonia and desquamative interstitial pneumonia represent different aspects of the same condition. Their varied morphological appearances probably reflect the fact that tissue has been taken at different stages in the development of the disease.