What Is Fibromuscular Dysplasia (FMD)?
FMD is a disorder that affects the walls of blood vessels or arteries. It is not a result of inflammation or plaque buildup.
Arteries are blood vessels that carry blood to different parts of the body. They often consist of strong, flexible cells.
But with FMD, the artery's cells become:
- Easier to damage.
Types of fibromuscular dysplasia
There are three types of FMD:
- Multifocal FMD. This is the most common type, in which the arteries look like a string of beads.
- Focal FMD. This affects about 10% of people with FMD. This type involves the narrowing of the arteries or lesions in the arterial wall.
- Adventitial FMD. A rare type that affects the outer layer of the artery.
FMD can happen in any artery but most commonly affects the:
- Renal arteries, which bring blood to your kidneys.
- Carotid arteries, which bring blood to your brain.
- Subclavian arteries, which bring blood to the upper part of your body.
- Vertebral arteries, which bring blood to the back of the brain.
In most cases, FMD can occur in more than one artery.
Fibromuscular dysplasia risk factors and causes
FMD can happen to anyone but is most common in women ages 25 to 50.
Doctors don't know exactly what causes FMD, but it likely has underlying factors like:
- Hormones. Most people with FMD are women.
- Mechanical stress from trauma, which places a physical strain on the arteries.
- Genes. FMD can run in families, although many people with FMD have no family history of it.
- Ehlers-Danlos syndrome (type IV). FMD can sometimes go hand in hand with this genetic connective tissue disorder.
- A lack of oxygen supplying the blood vessel walls. This causes the vessels to form fibrous lesions.
- Environment. Smoking and estrogen have known links to FMD.
Fibromuscular dysplasia complications
Some people with FMD have no symptoms. Symptoms depend on the blood vessels involved.
Even without symptoms, FMD can lead to severe, even life-threatening, complications. It can narrow the arteries that supply blood to the kidneys and brain.
Some complications of FMD include:
- Changes in kidney function. Reduced blood flow from narrowed arteries can damage the kidneys. You may have flank pain.
- High blood pressure. When the blood vessel narrows, the pressure on the artery walls increases.
- Torn arteries. Fibrous cells in the artery make them more prone to tears.
- Aneurysm, or a bulge or weak spot in an artery. Cell changes can weaken the artery walls, making them more likely to bulge.
- Stroke. When FMD affects the carotid or vertebral arteries, you may have a mini-stroke or stroke-like symptoms.
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