Fibromuscular dysplasia (FMD) of the arteries comprises a group of idiopathic, segmental, non-atherosclerotic and non-inflammatory diseases of the musculature of arterial walls that lead to stenoses of medium and small sized arteries. FMD most commonly involve the renal and cervico-cerebral arteries, usually leading to renal hypertension and cerebral ischemic symptoms respectively.
FMD is not a rare disease. The prevalence of symptomatic renal artery FMD is estimated at about 1/250 and that of symptomatic cervico-cerebral FMD is probably half of that. The familial forms are considered rare though, with an estimated prevalence of 1/2,500. In addition, stenoses may be associated with dissections or aneurysms, this association occurring only in 5 to 10% of cases. FMD predominantly affects women, with a female to male ratio of 3:1.
FMD can present at any age. Many people are asymptomatic and are usually diagnosed incidentally. In symptomatic cases, the clinical picture depends on the affected arterial bed. Most patients with renal artery involvement develop hypertension. Where present, renal artery dissection may lead to renal infarction and renal artery aneurysms may rupture causing internal hemorrhage. In case of cervico-cerebral involvement, stenosis or dissection may present as headaches, arterial bruit, pulsatile tinnitus, Horner's syndrome, transient ischemic attack or stroke. When present, intracerebral aneurysms may cause subarachnoid hemorrhage. Less commonly, FMD can involve the visceral, coronary or lower limb arteries and present as mesenteric ischemia, acute coronary syndrome, and claudication, respectively.
The etiology of FMD is unknown, although genetic, hormonal and mechanical factors have been suggested.
There is no biochemical test available for FMD. Diagnosis is based on non-invasive imaging tests including ultrasonography, magnetic resonance angiography and computed tomography angiography. The gold standard for diagnosing renal artery FMD is catheter angiography, but this invasive procedure is only used for patients in whom it is clinically pertinent to proceed with revascularization during the same procedure. Angiographic classification recognizes the multifocal (multiple stenoses on a given arterial segment displaying a 'string-of-beads' appearance) and unifocal types (solitary stenosis on a given arterial segment). Renal artery FMD is multifocal in more than 80% of patients. As different sites may be affected in a single patient, screening for FMD in other vascular territories is essential.
Differential diagnosis includes stenoses associated with artherosclerosis, arteritis, vasoconstriction and familial diseases such as vascular Ehlers-Danlos syndrome, Williams syndrome, Alagille syndrome, pseudoxanthoma elasticum, and neurofibromatosis type 1 (see these terms).
FMD is familial in 10% of cases.
The management of hypertensive patients with renal artery involvement includes antihypertensive medical therapy and, in case of resistance or intolerance to drugs, revascularization using percutaneous angioplasty or surgery. The prevention of ischemic events in symptomatic patients with cervico-cerebral involvement may require revascularization. If present, intra-cranial aneurysms may require surgical clipping or endovascular coiling.
With appropriate management and follow-up, most patients with FMD have a favorable long-term outcome.
Last update: December 2014
- Pr Xavier JEUNEMAITRE
- Pr Pierre-François PLOUIN