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Fibromuscular Dysplasia

by John W. Hallett, Jr., MD

Fibromuscular dysplasia includes a heterogenous group of nonatherosclerotic, noninflammatory arterial changes, causing some degree of vascular stenosis, occlusion, or aneurysm.

Fibromuscular dysplasia usually occurs in women aged 40 to 60. The cause is unknown. However, there may be a genetic component, and smoking may be a risk factor. Fibromuscular dysplasia is more common among people with certain connective tissue disorders (eg, Ehlers-Danlos syndrome type 4, cystic medial necrosis, hereditary nephritis, neurofibromatosis).

Medial dysplasia, the most common type, is characterized by alternating regions of thick and thin fibromuscular ridges containing collagen along the media. In perimedial dysplasia, extensive collagen deposition occurs in the outer half of the media. Fibromuscular dysplasia may affect the renal arteries (60 to 75%), carotid and intracranial arteries (25 to 30%), intra-abdominal arteries (9%), or external iliac arteries (5%).

Fibromuscular dysplasia is usually asymptomatic regardless of location. Symptoms, when they occur, vary by location:

  • Claudication in the thighs and calves, femoral bruits, and decreased femoral pulses when leg arteries are affected

  • Secondary hypertension when renal arteries are affected

  • Transient ischemic attack or stroke symptoms when carotid arteries are affected

  • Aneurysmal symptoms when intracranial arteries are affected

  • Rarely, mesenteric ischemic symptoms when intra-abdominal arteries are affected

Ultrasonography may suggest the diagnosis, but definitive diagnosis is made by angiography showing a beaded appearance (in medial or perimedial dysplasia) or a concentric band or long, smooth narrowing (in other forms).

Treatment varies by location. It may involve percutaneous transluminal angioplasty alone, percutaneous stent angioplasty, bypass surgery, or aneurysm repair. Smoking cessation is important. Control of other risk factors for atherosclerosis (hypertension, dyslipidemia, diabetes) helps prevent accelerated development of flow-limiting arterial stenoses.

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