Heart & vascular pathology
Ischemic disease
Fibromuscular dysplasia
Author: R. Amita, M.D.
Last author update: 1 February 2015
Last staff update: 19 September 2023
Copyright: 2015-2024, PathologyOutlines.com, Inc.
PubMed Search: Fibromuscular dysplasia [title] heart
Table of Contents
Definition / general | Sites | Etiology | Clinical features | Radiology description | Case reports | Treatment | Clinical images | Gross description | Microscopic (histologic) description | Microscopic (histologic) images | Differential diagnosis | Additional referencesCite this page: Amita R. Fibromuscular dysplasia. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/heartfibromusculardysplasia.html. Accessed December 25th, 2024.
Definition / general
- Fibromuscular dysplasia (FMD) is a vascular disease affecting small to medium sized vessels
- It is a noninflammatory, nonatherosclerotic condition occurring more frequently in younger individuals and women
Sites
- Renal artery involvement is most common (60 - 75%), followed by cervicocranial arteries (25 - 30%), visceral arteries (9%) and arteries in extremities (5%)
Etiology
- Rushton et. al. suggested it may be autosomal dominant with variable penetrance (Arch Intern Med 1980;140:233)
- Associated with hormonal factors, ergotamine preparations, methysergide, rubella syndrome
- Also heterozygous alpha-1-antitrypsin deficiency, pheochromocytoma, neurofibromatosis
- Ehlers-Danlos syndrome , Alport syndrome Type IV, cystic medial necrosis, coarctation of the aorta
Clinical features
- Symptoms occur when lesions are tightly stenotic producing hypoperfusion, if an associated aneurysm ruptures, if lesions embolize, thrombose or dissect
- Presenting symptoms include hypertension, headache, altered mentation, tinnitus, vertigo, neck pain
- Also transient ischemic attack, cerebral infarction, subarachnoid hemorrhage, syncope, Horner syndrome, cranial nerve palsies
- Deterioration of renal function is rare in fibromuscular dysplasia but common in atherosclerosis
- Overall, medial fibroplasia is the most common type of fibromuscular dysplasia, but in children, intimal fibroplasia is most common
Radiology description
- Angiographically a smooth focal stenosis (concentric band) or a long smooth (tubular) stenosis may be present
- "String of beads" describes its angiographic appearance, where the "bead" diameter is larger than the proximal vessel in medial fibroplasias
- Perimedial fibroplasia may also appear as arterial beading on an angiogram
- However, unlike medial fibroplasia, the caliber of the beads does not exceed that of the proximal artery and the beads are usually less numerous
- This dysplastic lesion results in severe stenosis and may be associated with collateral circulation
- Medial hyperplasia appears as a concentric, smooth stenosis on an angiogram, making it difficult to differentiate from intimal fibroplasia; sites of vessel involvement are similar to medial fibroplasia but do not affect branches of renal artery as often
Case reports
- Concomitant carotid, mesenteric and renal artery stenosis due to primary intimal fibroplasia (J Urol 1983;129:798)
- Woman with diffuse intimal fibromuscular dysplasia with multiorgan failure (Arch Intern Med 1996;156:2611)
Treatment
- Medical management to treat hypertension
- Antiplatelet agents
- Smoking cessation or other risk factor modification
- Endovascular therapy or surgery indicated if:
- Hypertension is poorly controlled despite maximum doses of three antihypertensive medications
- Patient is unable to tolerate medications or is noncompliant
- As an alternative to lifelong medication in this relatively young population
Clinical images
Images hosted on other servers:
Medial fibroplasia
Intimal fibroplasia
Gross description
- Medial fibroplasia:
- Involves distal 2/3 of main renal artery, occasionally extending into its branches
- Also commonly encountered in internal carotid artery at C1 and C2 vertebrae, compared to atherosclerosis which typically occurs at carotid bifurcation
Microscopic (histologic) description
- In 1971, a classification system to describe FMD of renal artery was proposed by Harrison and McCormack (Mayo Clin Proc 1971;46:161) based on dominant arterial wall layer involved:
- Intimal fibroplasia
- Medial dysplasia
- Adventitial (periarterial) fibroplasias
- Intimal fibroplasia:
- < 10% of all fibrous lesions
- Circumferential or eccentric deposition of collagen in intima but no lipid or inflammatory component
- Internal elastic lamina is identifiable but may be fragmented or duplicated
- This appearance may be mimicked by endarteritis due to inflammation or trauma
- Can occur as a generalized disorder involving renal, carotid, upper and lower extremity and mesenteric vasculature simultaneously mimicking a multisystem disease such as necrotizing vasculitis
- Medial dysplasia:
- Divided into medial fibroplasia, perimedial fibroplasia, medial hyperplasia
- Medial fibroplasia:
- A subtype of medial FMD, histologic finding in 75 - 80% of all cases of FMD
- Alternating areas of thinned media and thickened fibromuscular ridges containing collagen
- Some areas of internal elastic membrane are lost
- Perimedial fibroplasia:
- 10 - 15% of all lesions, found in young girls
- Extensive collagen deposition located in outer half of media and can replace it entirely, but does not extend beyond external elastic lamina
- Medial hyperplasia:
- True smooth muscle hyperplasia without fibrosis
- Found in 1 - 2% of all lesions
- Medial fibroplasia:
- Adventitial fibroplasias:
- Rarely seen (< 1%)
- Dense collagen replaces fibrous tissue of adventitia and may extend into surrounding tissue
- The other arterial layers and elastic laminae remain intact
Microscopic (histologic) images
Images hosted on other servers:
Medial fibroplasia
Differential diagnosis
- Intimal fibroplasia: necrotizing vasculitis
- Medial fibroplasia: atherosclerosis
Additional references
