Renal vascular smooth muscle proliferation in neurofibromatosis.

An unusual vascular lesion was seen in a 14-year-old white boy with renal vascular hypertension and neurofibromatosis. Microscopically, nodular intimal and medial proliferations of spindle-shaped cells involved arteries, arterioles, and veins of all caliber within the renal parenchyma. Immunoperoxidase studies indicated these cells to have characteristics of smooth muscle, and this finding was confirmed by ultrastructural examination. Despite the generalized nature of the process in the biopsy sample, the patient's hypertension responded well to surgical treatment.