Subendothelial electron-dense deposits in pulmonary alveolar wall in pulmonary actinomycosis.

Pulmonary actinomycosis is characterized by an extensive interstitial fibrosis of the lung in addition to granulomatous disease. I examined the fibrotic lung tissue of actinomycosis by electron microscopy and found subendothelial electron-dense deposits in the alveolar capillary wall. The meaning of this finding is discussed concerning the pathogenesis of interstitial fibrosis in pulmonary actinomycosis.