--- title: Fibromuscular dysplasia description: What fibromuscular dysplasia of the arteries is, which arteries it affects, why it can raise blood pressure and lead to stroke, how it is found, which treatment approaches guidelines describe, and when to call an ambulance. type: disease aliases: - FMD - fibromuscular dysplasia of the renal arteries - renal artery fibromuscular dysplasia - carotid artery fibromuscular dysplasia - string of beads sign sources: - tier: guideline org: minzdrav-rf title: Артериальная гипертензия у взрослых year: 2024 doi: 10.15829/1560-4071-2024-6117 url: https://cr.minzdrav.gov.ru/view-cr/62_3 - tier: guideline org: esc title: 2024 ESC Guidelines for the management of peripheral arterial and aortic diseases year: 2024 doi: 10.1093/eurheartj/ehae179 url: https://doi.org/10.1093/eurheartj/ehae179 - tier: guideline org: esc title: 2024 ESC Guidelines for the management of elevated blood pressure and hypertension year: 2024 doi: 10.1093/eurheartj/ehae178 url: https://doi.org/10.1093/eurheartj/ehae178 - tier: review title: First International Consensus on the diagnosis and management of fibromuscular dysplasia year: 2019 doi: 10.1097/HJH.0000000000002019 url: https://doi.org/10.1097/HJH.0000000000002019 - tier: reference org: msd-manuals title: Fibromuscular Dysplasia (MSD Manual Professional Version) year: 2025 url: https://www.msdmanuals.com/professional/cardiovascular-disorders/peripheral-artery-disorders/fibromuscular-dysplasia - tier: reference org: msd-manuals title: Fibromuscular Dysplasia (MSD Manual Consumer Version) year: 2025 url: https://www.msdmanuals.com/home/heart-and-blood-vessel-disorders/peripheral-artery-disorders/fibromuscular-dysplasia - tier: reference org: msd-manuals title: Renovascular Hypertension (MSD Manual Professional Version) year: 2025 url: https://www.msdmanuals.com/professional/cardiovascular-disorders/hypertension/renovascular-hypertension sources_checked: 2026-10-14 review: null --- Fibromuscular dysplasia (FMD) is a disease of the artery wall that is related neither to atherosclerosis nor to inflammation: the wall of the artery becomes abnormally thick, and the artery narrows and sometimes becomes blocked or widens to form an aneurysm. FMD most often affects the kidney (renal) arteries and the arteries of the neck, the carotid and vertebral arteries, but it can involve almost any artery, and several are often affected at once. FMD often causes no symptoms; when there are symptoms, they depend on which artery is affected.

The diagram shows a segment of an artery cut lengthwise: its initial part is on the left, and its middle and far parts are on the right. This could be, for example, a renal or carotid artery, the arteries FMD affects most often. The healthy artery is drawn with an even lumen all along.

In the most common form, multifocal FMD, narrowings alternate with widenings in the middle and far parts of the artery; on a scan this looks like a string of beads. The initial part of the artery is usually spared, unlike in atherosclerosis, which mainly affects that part. There is no plaque in the diagram: FMD is not atherosclerosis.

## Why it happens The cause of FMD is unknown. Both inherited and environmental factors probably play a role; smoking may be a risk factor. FMD occurs mainly in young and middle-aged women, but it is found at any age and in both women and men. According to the 2019 international consensus, about 80–90% of people with FMD are women. More than half of people with FMD have several arteries affected; besides narrowings, they may have dissections, aneurysms and marked tortuosity (twisting) of the arteries. Narrowing of a renal artery is more often caused by atherosclerosis, and FMD is the second most common cause; see the article on [renal artery stenosis](../renal-artery-stenosis/). The Russian Ministry of Health guideline describes two variants: multifocal FMD (80–90%), with alternating areas of stenosis and dilatation in the middle and distal segments of the artery (the "string of beads" sign), and focal FMD (10–20%), with a stenosis of varying length in any part of the artery. The 2019 international consensus proposes classifying lesions by their angiographic appearance only, as focal or multifocal FMD; the histopathological classification is no longer applicable in modern clinical practice. According to the consensus, FMD is primarily a stenotic disease: the diagnosis requires at least one focal or multifocal lesion, and the presence of aneurysm, dissection or tortuosity alone is not enough. According to the consensus, men may have a more aggressive course, with more frequent aneurysms and dissections. There is no genetic test specific to FMD, and the consensus sees no justification for genetic testing of asymptomatic relatives. ## Symptoms - **Renal arteries.** The most common sign is high blood pressure. For more about it, see the article on [hypertension](../hypertension/). - **Neck arteries (carotid and vertebral).** Symptoms are often non-specific: headache, often migraine-like, a pulsing sound in the ears in time with the heartbeat (pulsatile tinnitus), and dizziness. A transient ischaemic attack (TIA) or stroke can occur; these are usually attributed to dissection of the carotid artery. - **Brain arteries.** In people with FMD, aneurysms of the brain arteries are significantly more common than in other people. - **Arteries of the gut and legs.** Rarely there is vomiting or abdominal pain, and when the leg arteries are affected, pain, cramping or tiredness in the leg muscles (intermittent claudication). The 2019 consensus lists clinical features of renal artery FMD that warrant imaging: hypertension before 30 years of age, especially in women; resistant hypertension; a unilateral small kidney without a urological cause; an abdominal bruit without atherosclerosis or its risk factors; suspected renal artery dissection or infarction; and FMD in another vascular bed. Features of cerebrovascular FMD according to the consensus: severe or chronic migraine, pulsatile tinnitus, a cervical bruit, stroke, TIA or amaurosis fugax, and unilateral head or neck pain or focal neurological findings suggestive of cervical artery dissection. FMD is common among patients with [spontaneous coronary artery dissection](../spontaneous-coronary-artery-dissection/) (SCAD). ## How it is diagnosed FMD is diagnosed from images of the blood vessels. When renal artery FMD is suspected, the international consensus advises starting with CT angiography, or MR angiography if CT angiography is contraindicated. Ultrasound may suggest FMD, but the definitive diagnosis is made by angiography. The most accurate test is catheter angiography, in which contrast is injected through a catheter straight into the artery; it is done when the result may change treatment. FMD often affects several arteries, so everyone with FMD is advised to have whole-body CT angiography (MR angiography if it is contraindicated) at least once in their life, to find other affected arteries, aneurysms and dissections. The consensus advises the same imaging of the arteries from head to pelvis at least once for everyone who has had SCAD. The consensus accepts duplex ultrasound as the first diagnostic test for renal artery FMD only in specialised centres with extensive expertise; according to MSD, non-invasive testing is less reliable in FMD because the stenosis typically lies in the intrarenal portion of the artery. ## How it is treated FMD is a chronic disease of the blood vessels that needs treatment and regular follow-up. Blood pressure is managed according to the general rules, as in any hypertension. If you smoke, it is important to stop. If there are other risk factors for atherosclerosis, such as high blood pressure, high cholesterol or diabetes, they may also need treatment. There are not yet any studies that have tested the benefit of medicines specifically in FMD. Whether medicines are needed, and which ones, is decided by a doctor. Do not start, stop or change medicines on your own. For renal artery FMD with high blood pressure and a significant narrowing, guidelines suggest considering balloon angioplasty: the narrowed section is widened with a balloon from inside the artery. In FMD a stent is placed only in special cases, for example when the procedure causes a complication; details are in the block for students. After angioplasty, blood pressure returns to normal in some people, more often in younger people whose high blood pressure began recently. Open surgery is rarely done: for a complex lesion where the artery branches, for a narrowing combined with a complex aneurysm, or if angioplasty has not helped. Whether a procedure is needed, and which one, is decided by the doctor together with the patient. According to the consensus, people with FMD are followed up long term by a doctor familiar with the disease, and follow-up is more intensive during pregnancy. Sources word their approach to stenting in renal artery FMD differently. ESC (HTN): renal artery angioplasty without stenting should be considered for patients with hypertension and haemodynamically significant renal artery stenosis due to FMD (IIa C). ESC (PAAD): in hypertension and/or signs of renal dysfunction due to FMD, with high-risk features and signs of kidney viability, revascularisation with primary balloon angioplasty and bailout stenting should be considered (IIa B). The Russian Ministry of Health guideline does not recommend stenting in renal FMD except for flow-limiting dissection during the procedure or a renal artery aneurysm. Consensus: angioplasty alone is the revascularisation approach of choice, and stenting is reserved for treatment of procedural complications. ## When to call an ambulance The international consensus advises people with FMD to know the warning signs of TIA, stroke and arterial dissection, in the neck arteries or the heart arteries, and to seek medical care immediately if any of them appear. FMD of the carotid arteries can show up as a TIA or stroke: difficulty speaking, muscle weakness, paralysis of one side of the body, or vision problems. If there are signs of a stroke, call an ambulance straight away on your local emergency number (112 in the EU, 911 in the US and Canada, 999 in the UK); how to recognise them is described in the article on [carotid artery stenosis](../carotid-artery-stenosis/). Pain on one side of the head or neck, or neurological signs such as a drooping eyelid and a constricted pupil on the same side, may point to dissection of a neck artery. In this case, too, call an ambulance straight away. SCAD, a tear in the wall of a heart artery, is an uncommon cause of heart attack, and FMD is often found in people who have it. For its signs, see the article on [spontaneous coronary artery dissection](../spontaneous-coronary-artery-dissection/). As with any heart or blood vessel condition, call an ambulance for fainting, chest pain or severe shortness of breath: this is the site's general safety rule, repeated at the bottom of every page.