[Latent alveolitis in systemic disease. The transition between the normal and the pathological]

Alveolitis, an accumulation of inflammatory and immune cells in the alveolar structures, is the essential anatomical lesion associated with the development of pulmonary fibrosis. Broncho-alveolar lavage enables the detection of an alveolitis in patients without any respiratory disorder but having known pathology which can frequently lead to interstitial pneumonia, (certain systemic diseases). The cellular analysis of the bronchoalveolar lavage enabled two types of latent alveolitis to be identified: a lymphocytic alveolitis is very frequent during the course of extra-thoracic sarcoidosis, Crohn's disease, primary biliary cirrhosis, Sjögren-Gougerot syndrome, acute systemic lupus erythematosus and rheumatoid disease. A polymorphonuclear neutrophil alveolitis with or without an associated lymphocytosis which confirmed the almost exclusive attribute of either scleroderma, dermatopolymyositis or Sharp's syndrome. The role of alveolar macrophages is shown to be essential by the secretion of free oxygen radicals, chemotactic factor for polymorphonuclear neutrophils and for fibroblasts proliferation factors (fibronectin, fibroblastic growth factor). The significant and prognostic value of latent alveolitis remains poorly understood. A prolonged follow up of patients shows that the existence of a polymorpho-nuclear alveolar neutrophilia or of secretions containing fibronectin and free oxygen radicals from the alveolar macrophages is associated with a progressive deterioration of respiratory function. In summary the evidence of latent alveolitis in asymptomatic patients leads to the hope that in the future early therapeutic intervention may be instituted before the development of irreversible anatomical lesions.