An introduction to the interstitial lung diseases.

The interstitial lung diseases are a heterogeneous group of disorders that have similar clinical, roentgenographic, and physiologic features. The histopathology of most is characterized by an alveolitis and alveolar septal fibrosis. Current concepts are that connective tissue alterations are preceded and caused by the alveolitis. Clinicopathologic correlative data indicate that patients with an active alveolitis with minimal fibrosis are most likely to respond to treatment. Those patients with minimal alveolitis and severe fibrosis are unlikely to respond to treatment. Although lung biopsy is the standard for assessing the severity of alveolitis, chest roentgenograms and pulmonary function testing can be useful in some diseases. Recently, gallium lung scanning and bronchoalveolar lavage have emerged as promising monitors of disease activity. Gallium scans appear to be useful, but additional studies are needed. Although bronchoalveolar analysis will probably be a valuable aid in managing patients with interstitial disease, it cannot be recommended in the routine evaluation of these patients.