Tubular Structures in Pulmonary Endothelial Cells in Systemic Lupus Erythematosus

A case of systemic lupus erythematosus with associated diffuse interstitial pulmonary fibrosis is presented. Electron microscopic study of a biopsy of lung tissue revealed multiple aggregates of tubular structures approximately 250 A in diameter within the cytoplasm of capillary endothelial cells. Their size and location suggest that they probably represent a reaction to injury of a cytoplasmic component of the cell. However, since their morphology is similar to that of the nucleocapsid of myxoviruses, the possibility that they are of viral origin must be entertained.