Fibromuscular dysplasia

'''For patient information page, click here

Associate editor in Chief: Shantanu Sinha, MD,FACC

Overview
Fibromuscular dysplasia (FMD) is a disease that can cause stenosis of the renal arteries, carotid arteries, and less commonly, the arteries of the abdomen. The disease can cause hypertension, strokes, and arterial aneurysm and dissection.

In individuals with FMD, the walls of one or more arteries undergo dysplasia. Due to this abnormal cellular development, the vessels may become stenosed. A sufficient decrease in blood flow through the artery can cause symptoms. However, FMD is often diagnosed incidentally in the absence of any signs or symptoms during an imaging study. Angiography with contrast will show a characteristic "string of beads" morphology in a vessel affected by FMD.

Epidemiology
Fibromuscular dysplasia tends to occur in females between 14 and 50 years of age. However, it has been found in children under the age of 14, both male and female.

Pathology
Fibromuscular dysplasia is characterized by fibrous thickening of the intima, media, or adventitia of the renal artery. Up to 75% of all patients with FMD will have disease in the renal arteries (Fenves, 1999). The lesions cause narrowing of the artery lumen. The second most common artery affected is the carotid artery, which is found in the neck and supplies the brain with blood. Less commonly, FMD affects the arteries in the abdomen (supplying the liver, spleen and intestines) and extremities (legs and arms). More than one artery may have evidence of FMD in 28% of people with this disease (Luscher, 1986). All arteries should be checked if found.

Signs and Symptoms
As a result of renal artery stenosis, the kidney's afferent arteriolar pressure falls. The renin-angiotensin system is activated, causing fluid retention and hypertension. Symptoms of craniocervical involvement include headaches and lightheadedness, although patients are often asymptomatic. On physical examination, one may detect neurological symptoms secondary to a stroke, a bruit over an affected artery, and diminished distal pulses.

Treatment
ACE inhibitors, and Angiotensin II receptor antagonists are often initial treatments of fibromuscular dysplasia. Refractory cases are often treated by balloon angioplasty or stenting of the renal artery. Besides high blood pressure control, anti-platelet drugs and blood thinner drugs may be used. Bypass surgery is a considered treatment and also vein replacement.