Fibromuscular dysplasia classification
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Mohsen Basiri M.D.
Overview
- The classification system for fibromuscular dysplasia (FMD) was first according to the arterial layer involved. (tunica intima, tunica media , or adventitia) . However, with use of transluminal percutaneous angioplasty (TPA) for treatment of FMD lesions and its preference rather than surgery, the obtaining of pathological specimens are restricted. Thus, today, FMD is a disease diagnosed radiographically and histopathological classification has been replaced by the arteriographic findings.
Classification
Fibromuscular dysplasia may be classified according to angiographic findings or histological characteristics, as below:
Angiografic classification [1]
- Multifocal FMD
- With angiographic appearance of a "string of beads" due to multiple areas of stenosis and dilatation(image?) this subtype corresponds pathologically to medial fibroplasia.
- Focal FMD
- This form is less common , and it has the angiographic appearance of a "circumferential or tubular stenosis" and corresponds pathologically to intimal fibroplasia, medial hyperplasia and periarterial hyperplasia are histologic types that may also have a focal appearance.
It has been shown that these two different angiographic subtypes of FMD (multifocal and focal) have different phenotypic presentations and natural history.[2]
Histological classification
In this classification system, FMD is categorized according to the arterial layer involved.
- Medial dysplasia
- Medial dysplasia is the most common type of FMD, and accounting for more than eighty percent of fibromuscular lesions. Medial FMD is further subdivided into three subtypes: medial fibroplasia, perimedial fibroplasia, and medial hyperplasia.
. Medial fibroplasia microscopically is accompanied by alternating areas of thinned and thickened media. thickened area are fibromuscular ridges containing collagen as well thinned areas are due to smooth muscle and internal elastic lamina loss with resultant arterial stenosis alternating with dilatation.
This subtype corosponds angiographically to the classic "string of beads" appearance .
Perimedial fibroplasia is associated with collagen deposition in the outer half of the media; and medial hyperplasia, in which there is true smooth muscle hyperplasia without significant fibrosis as well as collagen deposition[3]
- Intimal fibroplasia is caused by circumferential or eccentric deposition of collagen in the intima . The internal elastic lamina may be intact, fragmented, or duplicated. There is no inflammatory or lipid component. this subtype corresponds angiografically to Focal FMD.
- Adventitial disease, a rare manifestation of FMD, is caused by replacement of fibrous tissue of dventitia with dense collagen, collagen deposition may extend into the periarterial tissue, with accompanying inflammation and focal infiltration of lymphocytes.
References
- ↑ Persu A, Touze E, Mousseaux E, Barral X, Joffre F, Plouin PF. Diagnosis and management of fibromuscular dysplasia: an expert consensus. Eur J Clin Invest. 2012;42:338–347
- ↑ Sebastien Savard, Olivier Steichen, Arshid Azarine, Michel Azizi, Xavier Jeunemaitre & Pierre-Francois Plouin (2012). "Association between 2 angiographic subtypes of renal artery fibromuscular dysplasia and clinical characteristics". Circulation. 126 (25): 3062–3069. doi:10.1161/CIRCULATIONAHA.112.117499. PMID 23155180. Unknown parameter
|month=ignored (help) - ↑ Stanley JC, Gewertz BL, Bove EL, Sottiurai V, Fry WJ (May 1975). "Arterial fibrodysplasia. Histopathologic character and current etiologic concepts". Arch Surg. 110 (5): 561–6. PMID 1131001.