The "string-of-beads" feature in medial fibromuscular dysplasia. The sign is caused by areas of relative stenoses alternating with small aneurysms. The diameters of the aneurysms exceed the normal diameter of the artery. The sign is characteristic of medial FMD. A similar bead appearance may be seen in perimedial FMD, but the diameters of the beads do not exceed the normal diameter of the artery [10]. Note the involvement of branch renal arteries.
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Pierre-François Plouin, Jérôme Perdu, Agnès La Batide-Alanore, Pierre Boutouyrie, Anne-Paule Gimenez-Roqueplo, Xavier Jeunemaitre. Fibromuscular dysplasia. Orphanet Journal of Rare Diseases. 2, 28. 2007. <a class="external mw-magiclink-pmid" rel="nofollow" href="//www.ncbi.nlm.nih.gov/pubmed/17555581?dopt=Abstract">PMID 17555581</a>. (<a rel="nofollow" class="external free" href="http://www.ojrd.com/content/2/1/28">http://www.ojrd.com/content/2/1/28</a>)