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Fibromuscular Dysplasia (FMD) is a non-inflammatory, non-atherosclerotic vascular disease that causes abnormal cellular proliferation and fibrosis within the arterial wall.
It leads to stenosis, aneurysm, dissection, or tortuosity of medium-sized arteries, most commonly affecting the renal and carotid arteries.
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https://www.youtube.com/watch?v=USngX_kuves
| Layer Involved | Effect |
|---|---|
| Media (most common) | Alternating areas of fibrosis and thinning → stenosis + aneurysmal outpouchings |
| • Leads to string-of-beads appearance due to alternating stenoses and dilations | |
| Intima or Adventitia | Less common; can cause focal stenosis |
Unlike atherosclerosis, FMD affects younger patients and spares vessel origins
| Parameter | Details |
|---|---|
| Prevalence | ~0.5–1% (often underdiagnosed) |
| Sex predilection | 90% women, typically age 30–50 |
| Most affected arteries | Renal arteries (~60–75%) > Carotid/Vertebral arteries (~25–30%) |
| Associations | Possible genetic predisposition; no clear inflammatory markers |
Renal Artery FMD:
| Symptom | Mechanism |
|---|---|
| Refractory hypertension | Renal ischemia → ↑ renin |
| Abdominal bruit | Turbulent flow in renal artery |
| Renal insufficiency | Rare unless bilateral or progressive |
Carotid/vertebral artery FMD:
| Symptom | Mechanism |
|---|---|
| Headache (pulsatile) | Vascular irritation |
| Tinnitus | Turbulent flow |
| Dizziness, neck pain | Arterial dissection |
| TIA/stroke | Embolism or reduced flow from stenosis/dissection |