A morphological study of primary pulmonary hypertension--an analysis of six autopsy cases.

Six typical autopsy cases of primary pulmonary hypertension are reported. The histopathological features were as follows: medial hypertrophy of the muscular pulmonary arteries, muscularization of arterioles, internal fibrosis and fibroelastosis of muscular pulmonary arteries with typical "onion-skin" configuration, fibrinoid necrosis of the media or necrotizing arteries of muscular pulmonary arteries, and formation of highly characteristic plexiform lesions and dilatation lesions. It is thought that the plexiform lesions seen in all six cases represent morphological changes resulting from pulmonary hypertension rather than congenital abnormalities or thromboembolism.