Most common form of fibromuscular dysplasia, comprises 75% of cases
Predominantly affects young women and affects the distal 2/3 of the main renal artery.
Gross: alternating thickened and thinned arterial walls give rise to the characteristic "sausage-string" or "string of beads" appearance (especially as seen on angiography) (image A).
Histology: fibromuscular thickening of the media alternating with areas of thinning and loss of the internal elastic lamina (image B).
Medial dissection may occur in up to 10% of cases.