Fibromuscular dysplasia

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 * Associate Editor-in-Chief: Shantanu Sinha, MD,FACC

Synonyms and keywords: FMD

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.

Age
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.

Sex
Fibromuscular dysplasia affects females more than males.

Pathophysiology
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. 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. 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. All arteries should be checked if FMD is found in one vascular bed. 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.

Risk Factors

 * Sex. Women have a much greater risk than men.
 * Age. more common in people from 25 to 50 years old.
 * Smoking is associated with a higher risk of developing fibromuscular dysplasia. For those already diagnosed with the disease, smoking increases further risk.

Causes

 * Genetics. Genetics may play a role in the development of fibromuscular dysplasia. But, if another family member has fibromuscular dysplasia, you or a relative may never get fibromuscular dysplasia, or you might get the condition in a different artery or have a milder case or a more severe case than your family member's fibromuscular dysplasia. In addition, not everyone who has fibromuscular dysplasia has a relative with the disease.
 * Hormones. Premenopausal women have this disease more often than men do.

Symptoms
Patients are often asymptomatic, but they may complain of the following:
 * High blood pressure
 * Dizziness or vertigo
 * Chronic headache
 * Intracranial aneurysm
 * Ringing in the ears
 * Weakness or numbness in the face
 * Neck pain
 * Changes in vision

Neck

 * Carotid bruit may be present

Abdomen

 * Abdominal bruit may be present

Angiography
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.

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 can be considered.