Fibromuscular dysplasia (FMD), a disease that primarily affects young to middle-aged women, is characterized by the proliferation of connective tissue and muscle fibers within the arterial vessel walls.

Epidemiology

Etiology

Pathophysiology

Fibromuscular dysplasia (FMD) is an idiopathic, non-inflammatory, non-atherosclerotic, developmental condition that primarily affects small and medium-sized muscular arteries.

• FMD results in ischemia by one or more of the following mechanisms:
  • Stenosis
  • Formation of saccular aneurysms → aneurysmal rupture
  • Arterial dissection → arterial occlusion
• Renal artery stenosis → ↓ renal perfusion → compensatory activation of the renin–angiotensin–aldosterone system → secondary hypertension
• Disease localization
  • Renal artery (renal FMD; ∼ 75–80% of cases)
    • Usually bilateral renal artery stenosis
  • Carotid and vertebral artery involvement (extracranial cerebrovascular FMD; ∼ 65–75% of cases and often bilateral)

Clinical features

• Renal FMD
  • Clinical features of renal artery stenosis
    • Secondary hypertension
    • Abdominal bruit
    • Symptoms of chronic kidney disease
  • Flank or abdominal pain
• Cerebrovascular FMD
  • Headache, neck pain, pulsatile tinnitus
  • TIA, amaurosis fugax, stroke, Horner's syndrome
  • Cervical bruit

Diagnostics

• Best initial tests for renal FMD: duplex ultrasonography and/or CT angiography
  • Common finding: “string of beads” sign
• Differential diagnostics
  • Atherosclerosis (Renal artery stenosis)
    • Patients with atherosclerosis are usually older, male, and have risk factors such as obesity and/or cigarette smoking.
    • On angiography, atherosclerosis affects the proximal 1/3 of arteries, while FMD affects distal 2/3 of the artery.

Treatment