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
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 of fibromuscular dysplasia 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 of fibromuscular dysplasia 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.