Fibromuscular dysplasia (FMD) is an arterial disease of unknown etiology typically affecting the medium and large arteries of young to middle-aged women.
There are 3 types of FMD: intimal, medial, and subadventitial (perimedial) but this is not easily differentiated on CT/angiography. It is often asymptomatic but can be associated with spontaneous dissection.
3 CT/angiographic findings:
This is the most common form. Angiography reveals the typical "string-of-beads" appearance, with alternating segments of stricture and dilation. This type is usually a result of medial fibroplasia of the arterial wall.
Less commonly a long tubular stenosis may be seen. This is associated with any of the histologic types, but it is most commonly seen with the intimal form.
This unusual form is characterized by involvement of only 1 side of an artery. May lead to saccular aneurysms and can be difficult to distinguish from atherosclerotic ulceration and pseudoaneurysm.