DESQUAMATIVE INTERSTITIAL PNEUMONIA AND IDIOPATHIC DIFFUSE PULMONARY FIBROSIS

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Abstract
Seven cases of the idiopathic diffuse fibrosing alveolitis are reported. Five of them were identified as being of the desquamative interstitial pneumonia type while 2 belong to the more commonly known diffuse interstitial fibrosis of Hamman-Rich type. The lung sections of these and of the 2 previously reported cases were examined with special methods including PAS and iron staining. A series of lung sections from patients who died of mitral valve stenosis were also examined for comparison. One of the latter cases had in conjunction with long-standing mitral stenosis a concomitant presence of advanced diffuse pulmonary fibrosis of the desquamative interstitial pneumonia type. The bronchiolectatic air spaces were filled with typical desquamated "granular pneumocytes," but contrary to the original description of these cells they stained also intensely blue for iron, which appeared as a dark diffuse blue, a granular pattern, or a mixture of the two. This proved to us that there is basically no difference between the so-called "granular pneumocytes" and the pulmonary macrophages. Both seem to represent the same mesodermal alveolar septal cells (Lange) with a high capability for phagocytosis. The appearance of these cells seems to vary with the particular biologic function they may have to perform. In cases under discussion the additional function of a "granular pneumocyte" is to dispose iron from decayed red blood cells in bronchiolectatic spaces. The literature shows that this unexpected finding of iron in the "granular pneumocytes" could cause confusion when trying to diagnose a case as desquamative interstitial pneumonia. The etiologies of diffuse interstitial pulmonary fibrosis and desquamative interstitial pneumonia have not been clarified, but the roentgenographic findings and tissue sections show that there is a definite overlap between these two. The authors conclude that both types can progress into the similar appearing, far-advanced final stage, once considered to be the very rare entity, "muscular cirrhosis of the lung." Their term "muscular cirrhosis of the lung" should not be used for hamartomatous myomatosis where there is no underlying fibrosing process in the alveolar wall. The roentgenologic, clinical, pathophysiologic, histopathologic and etiologic aspects of this disease are discussed.

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