Fibromuscular dysplasia classification: Difference between revisions

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==Overview==
==Overview==
The classification system for fibromuscular dysplasia (FMD) was first according to the arterial layer involved. (intima, media, or adventitia) . However, with use of TPA for treatment 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are restricted.Thus,today, FMD is a disease diagnosed radiographically and histopathological classification has been replaced by an arteriographic findings . Olin JW, Gornik HL, Bacharach JM, et al. Fibromuscular dysplasia: state of the science and critical unanswered questions: a scientific statement from the American Heart Association. Circulation 2014; 129:1048.
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 Thus, today, FMD is a disease diagnosed radiographically and histopathological classification has been replaced by the [[Arteriography|arteriographic]] findings.
20. Lüscher TF, Lie JT, Stanson AW, et al. Arterial fibromuscular dysplasia. Mayo Clin Proc 1987; 62:931
Historically, FMD has been classified histopathologically into
categories based on the dominant arterial layer involved
(media, intima, or adventitia) and the composition of the
arterial lesion (collagen deposition, known as fibroplasia, or,
less commonly, hyperplasia of smooth muscle cells).


==Classification==
==Classification==
Fibromuscular dysplasia may be classified according to [[Angiogram|angiographic]] findings or histological characteristics, as below.
Fibromuscular dysplasia may be classified according to [[Angiogram|angiographic]] findings or [[histological]] characteristics, as below:


=== Angiografic classification ===
'''Angiografic classification:''' <ref>Persu A, Touze E, Mousseaux E, Barral X, Joffre F, Plouin PF. Diagnosis
*'''Multifocal FMD'''
and management of fibromuscular dysplasia: an expert consensus. Eur J
**With [[Angiogram|angiographic]] appearance of a "string of beads" due to multiple areas of [[stenosis]] and dilatation(image; this subtype corresponds pathologically to medial fibroplasia.
Clin Invest. 2012;42:338–347</ref>
*'''Focal FMD'''
*Multifocal FMD
**This form is less common (image 2), 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.
**With [[Angiogram|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 [21]. 21. Savard S, Steichen O, Azarine A, et al. Association between 2 angiographic subtypes of renal artery 􀉹bromuscular dysplasia and clinical characteristics.Circulation 2012; 126:3062.
It has been shown that these two different angiographic subtypes of FMD (multifocal and focal) have different phenotypic presentations and natural history.<ref>{{Cite journal
This has led some investigators to question whether FMD is, in fact, a single disease [22]. Olin JW. Is 􀉹bromuscular dysplasia a single disease? Circulation 2012;126:2925.
| author = [[Sebastien Savard]], [[Olivier Steichen]], [[Arshid Azarine]], [[Michel Azizi]], [[Xavier Jeunemaitre]] & [[Pierre-Francois Plouin]]
| title = Association between 2 angiographic subtypes of renal artery fibromuscular dysplasia and clinical characteristics
| journal = [[Circulation]]
| volume = 126
| issue = 25
| pages = 3062–3069
| year = 2012
| month = December
| doi = 10.1161/CIRCULATIONAHA.112.117499
| pmid = 23155180
}}</ref>


=== Histologic classification ===
=== Histological classification: ===
*'''Medial fibroplasia'''
In this classification system, FMD is categorized according to the arterial layer involved.
**This type of FMD represents the most common dysplastic lesion, accounting for more than 80 percent of fibromuscular lesions [18,19]. Angiographically, medial fibroplasia is characterized by the classic "string of beads" appearance (image 1). This appearance is due to alternating fibromuscular webs and aneurysmal dilatation. In areas of dilatation, the internal elastic lamina is absent, which is possibly the primary defect. Total occlusion is uncommon. <ref name="pmid1131001">{{cite journal |vauthors=Stanley JC, Gewertz BL, Bove EL, Sottiurai V, Fry WJ |title=Arterial fibrodysplasia. Histopathologic character and current etiologic concepts |journal=Arch Surg |volume=110 |issue=5 |pages=561–6 |date=May 1975 |pmid=1131001 |doi= |url=}}</ref>


*Intimal fibroplasia (which accounts for approximately 10 percent of FMD) is caused by circumferential or eccentric deposition of collagen in the intima (image 2). The internal elastic lamina may be intact, fragmented, or duplicated, the latter especially in the childhood form. There is no inflammatory or lipid component.
'''Medial dysplasia'''
*Medial [[dysplasia]] is the most common type of FMD and is 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 [[Anatomical terms of location|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 corresponds 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<ref name="pmid1131001">{{cite journal |vauthors=Stanley JC, Gewertz BL, Bove EL, Sottiurai V, Fry WJ |title=Arterial fibrodysplasia. Histopathologic character and current etiologic concepts |journal=Arch Surg |volume=110 |issue=5 |pages=561–6 |date=May 1975 |pmid=1131001 |doi= |url=}}</ref>


*In perimedial fibroplasia, which occurs predominately in children, large parts of the media (in particular, the outer zone) are replaced by collagen, with irregular thickening of the media. Total occlusion may occur with development of collateral vasculature. "Beading" is present in this type, but the "beads" are less numerous and are smaller than in medial fibroplasia. Aneurysm formation is uncommon.
==== '''Intimal fibroplasia''' ====
*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.


*Medial hyperplasia, a rare manifestation, is caused by smooth muscle cell hyperplasia without fibrosis.
==== Adventitial  disease ====
*Periarterial hyperplasia, also a rare manifestation, is caused by expansion of the fibrous adventitia; collagen extends into the periarterial fat, with accompanying inflammation
*Adventitial  disease, a rare manifestation of FMD, is caused by replacement of [[fibrous tissue]] of [[Adventitia|adventitia]] with dense [[collagen]], collagen deposition may extend into the periarterial tissue, with accompanying [[inflammation]] and focal [[Infiltration (medical)|infiltration]] of [[lymphocytes]].


==References==
==References==

Latest revision as of 22:16, 19 August 2018

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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 is 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 corresponds 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

  • 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

References

  1. 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
  2. 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)
  3. 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.

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