Fibromuscular dysplasia – A cause of arterial disease

Fibromuscular dysplasia (FMD) is a disorder that affects the arteries making them prone to stenosis, occlusion, aneurysm or dissection. The disease can virtually affect any artery, but the renal and carotid arteries are affected more often, followed by vertebral, visceral and iliac arteries. It is most common in females (90% of the cases among adults) and can affect patients of all age groups.

CLINICAL PRESENTATION:

The presentation varies depending on the arteries affected. Renal artery involvement may lead to hypertension and/or decline in GFR. Carotid or vertebral disease may lead to neurological symptoms (headache, tinnitus, TIA or stroke). Peripheral disease may present as claudication.

CLASSIFICATION:

FMD can be classified by its angiographic appearance in:

Multifocal: It has a “String of beads” aspect. It is the most common type and it corresponds histologically to medial fibroplasia.

Focal: A localized area of tubular or circumferential stenosis. It corresponds histologically to intimal or adventitial fibroplasia.

DIAGNOSIS:

The condition should be suspected in patients with secondary hypertension, arterial bruits or in younger patients with symptoms of arterial insufficiency and no or few risk factors for atherosclerosis.

Diagnosis is confirmed by imaging. Duplex ultrasound or computed tomography angiography (CTA) can be used as noninvasive methods and are often enough to diagnose the condition. However, catheter-based digital subtraction angiography (DSA), although invasive, is the best test for definitive diagnosis.

Differential diagnosis include atherosclerosis and vasculitis. Atherosclerosis usually is present in older patients that have multiple risk factors (hypertension, dyslipidemia, smoking, diabetes), affecting the proximal areas and the bifurcations of the arteries. FMD, on the other hand, can affect distal segments. Vasculitis, unlike FMD, can be associated with systemic symptoms and changes in the CBC and acute phase proteins.

Patients with FMD in one area of the may be evaluated at least once for the presence of FMD in another areas with a magnetic resonance angiography.

MANAGEMENT:

Treatment depends on the area affected and the presence of symptoms or organ deterioration.

Asymptomatic, stable patients may not need treatment at all. Some professionals may use prophylactic aspirin in some cases to prevent thrombotic events.

Patients with renal involvement and hypertension do need treatment, initially with medication alone. Medications that can be used to treat hypertension in these patients are the same ones that can be used on the general population. However, GFR and potassium should be closely monitored in patients taking ACE inhibitors or ARBs due to the risk of decrease in GFR and hyperkalemia.

Revascularization as a treatment for renal disease may be considered for patients that cannot tolerate anti-hypertensive medications, those with resistant hypertension (BP above goal despite 3 medications in optimal doses) despite compliance, or bilateral disease or unilateral disease in patients with only one functional kidney with evidence of kidney function deterioration. Revascularization can also be considered for young patients with recent-onset hypertension in order to cure hypertension and avoid long-term organ damage and medication use.

Percutaneous transluminal angioplasty (PTA) is often the preferred revascularization method for renal artery disease. Unlike atherosclerosis, PTA for renal FMD often does not require stent placement. Surgical revascularization (aortorenal bypass) is usually reserved for patients with unfavorable anatomy or with unsuccessful PTA.

Regardless of treatment choice, patient should have the kidney function and renal artery assessed by ultrasound every six months.

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