Chronic interstitial pneumonia

Abstract

Despite an increased understanding of the various processes that can lead to pulmonary fibrosis, the chronic interstitial pneumonias continue to challenge and frustrate the pulmonary physician. Heitzman, in his book, has defined these conditions as 'a pulmonary reaction of known or unknown etiology, characterized by an interstitial inflammatory response that is usually followed by the development of reticular or collagen fibers or both within the interstitium.' This is understandable, since approximately one quarter of the lung is made up of connective tissue comprised of collagen elastic fibers, and proteoglycans. Of these, collagen is the most important, being identified in the tracheobronchial tree, vascular compartment, parenchyma, and pleura. In the interstitial space, collagen is synthesized by fibroblasts or 'mesenchymal cells' stimulated by such factors as lymphokines. The chronic interstitial pneumonias result from a variety of agents and processes with the lung reacting in a rather uniform pathologic fashion. Because of the prognostic and therapeutic differences involved, it becomes imperative to obtain an accurate history, especially of any occupational exposure, and pertinent laboratory studies including a lung biopsy. It is only when all this information has been obtained that pertinent therapeutic goals can be decided upon. Hopefully, these early exhaustive diagnostic efforts will help to influence our understanding of the course of these perplexing diseases.