Fibromuscular dysplasia is an idiopathic, segmental, nonatherosclerotic and noninflammatory disease of the muscle layer of arterial walls that leads to stenosis of small- and medium-sized arteries. Fibromuscular dysplasia preferentially affects young women. Although it can affect every arterial tree, it most often touches the renal and internal carotid arteries. Renal fibromuscular dysplasia can cause hypertension by stenosis of the renal artery, most often seen on angiography as resembling a "pearl necklace". Cerebrovascular fibromuscular dysplasia becomes symptomatic when the arterial stenosis is tight and causes hypoperfusion, embolism, or thrombosis or when arterial dissection or rupture of the associated aneurysm occurs.