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:

Type 1

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.

Type 2

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.

Type 3

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.