[Pathogenesis of idiopathic pulmonary fibrosis]

Idiopathic pulmonary fibrosis or lone cryptogenic fibrosing alveolitis is an interstitial lung disease of unknown origin carrying an unfavorable prognosis. A yet unidentified hazard triggers a chronic inflammatory infiltration of the lung parenchyma characterized by an accumulation of alveolar macrophages, neutrophil and eosinophil granulocytes, and lymphocytes. Cytokines released by the activated cells modulate the inflammatory events. Oxidants and proteases, mainly released by alveolar macrophages and neutrophil granulocytes, mediate the injury to the lung parenchyma, leading to loss of alveolar-capillary units. The ensuing repair process, mesenchymal cell proliferation and up-regulation of synthesis of collagen fibers and other components of connective tissue matrix, replaces lung parenchyma by fibrotic tissue, leading to irreversible pulmonary dysfunction.