Medial defects of lung vessels: a new cause of pulmonary hypertension.

Defects, abrupt thinning of the media of muscular pulmonary arteries and pulmonary veins, were observed in two female patients, one 20 and the other 11 years of age. This congenital anomaly was associated with vasoconstriction and medial hypertrophy of adjacent segments of the vascular wall, as well as with a peculiar type of intimal proliferation. The subsequent intimal fibrosis was essentially limited to the hypertrophied segments and caused arterial obstruction and pulmonary hypertension in one of the patients. The other patient had concomitant arteriovenous fistulae, probably related to the extrahepatic portal hypertension that was also present. The medial defects of the pulmonary arteries and veins are likely to be congenital. They may easily be overlooked during histologic examination.