Fibromuscular dysplasia (FMD) is a non-inflammatory, non-atherosclerotic disorder of medium sized arteries of unclear cause.  Affected blood vessels demonstrate single or multiple areas of narrowing (stenosis).  It most commonly involves the arteries to the kidneys resulting in high blood pressure, aneurysms, and occasionally splitting (dissection) of the vessel wall.  The carotid and vertebral arteries to the brain are also frequently involved, which can lead to headache, pulsatile ringing in the ears, and stroke.  Other presentations include involvement of the intestinal arteries leading to abdominal pain and aneurysms, arteries to the arms or legs resulting in cramping or heaviness with use, and heart arteries leading to heart attack.  FMD is mostly seen in women, although men can have it as well.

The cause of FMD is unknown, and seemingly asymptomatic FMD is sometimes found when individuals have imaging scans for other reasons.  Examination of blood vessels from patients with FMD typically reveal abnormalities in the lining of the affected arteries or in the smooth muscle around the vessel.  It is not believed to be due to an autoimmune syndrome or to high cholesterol (atherosclerosis).  Studies have failed to identify a single genetic cause for the disorder, although it can run in families.  On rare occasion, FMD-type changes are seen in the blood vessels of patients with other vascular disorders such as Marfan’s Syndrome, Loeys-Dietz Syndrome, and Ehlers-Danlos Syndrome.  The disease appears to be worse in individuals who smoke.

FMD is diagnosed through a combination of non-invasive and invasive imaging studies.  Most cases are diagnosed non-invasively by computed tomography angiography (CTA) of the head, neck, chest, abdomen, and pelvis.  When CTA cannot be performed, magnetic resonance angiography (MRA) can be used instead.  Duplex ultrasonography (sonogram) can provide useful data on blood flow through affected arteries, although it is less sensitive for initial diagnosis.  In some cases, an invasive test known as an angiogram can be performed on suspected vessels.  In an angiogram, a flexible catheter is inserted into a blood vessel, x-ray contrast dye is injected, and x-ray pictures are taken of the affected vessels.  This is the most sensitive test for diagnosing FMD, although it entails more risk than non-invasive imaging studies.

The treatment of FMD varies depending on the blood vessels involved and an individual’s particular symptoms.  High blood pressure due to FMD of the kidney arteries can be treated with medications, and in many cases, we may be able to improve or cure the high blood pressure by opening the narrowed segments in the arteries.  Historically, surgery was often used to bypass the narrowed vessels.  Currently, surgery is very rarely performed, and patients are now treated with balloon angioplasty.  Other blood vessels- such as arteries to the brain- can be managed conservatively, with balloon angioplasty, or with surgery depending on the circumstances.  Aspirin is often prescribed, and individuals with splitting of the arterial walls may be treated with blood thinners.  In patients who smoke, smoking cessation is critically important.

Many physicians are unfamiliar with FMD, its diagnosis, and management.  Imaging studies and interventions for FMD cannot be interpreted and performed using criteria commonly applied to other vascular diseases.  It is important to seek evaluation at a center experienced in the care of FMD.