Fibromuscular Dysplasia – Causes, FMD, and Arterial Vascular Disease of the Renal Arteries

Fibromuscular dysplasia is a non-inflammatory arterial wall disorder. In this condition, various layers of the affected artery’s wall become thickened due to accelerated growth of muscle and connective tissue. This thickening of the arterial wall can occur throughout the body. The result is a narrowing of the affected artery—medically known as stenosis—or, rarely, a complete blockage of the vessel.

According to ICD code I77.3, fibromuscular dysplasia is classified as one of the “Other diseases of arteries and arterioles.”

The vessel wall consists of connective tissue and muscle. When these thicken, the vessel’s cross-sectional area decreases © Alex Mit | AdobeStock

The majority of patients with fibromuscular dysplasia do not experience any symptoms. However, it is generally possible for symptoms associated with vascular narrowing to occur.

These include pain in the affected areas, such as

• headaches in cases of stenosis in the head region or
• intermittent claudication in cases of vascular stenosis in the pelvis or legs.

Angina pectoris may also occur. This condition is characterized by episodic chest pain.

If fibromuscular dysplasia affects the renal arteries, the kidneys receive insufficient blood flow. Over time, this leads to high blood pressure, which is caused by reduced blood flow to the kidneys. This condition is referred to as renal hypertension.

The exact cause of fibromuscular dysplasia is currently unknown. However, medical professionals believe that a genetic predisposition plays a role. It has been observed that fibromuscular dysplasia occasionally runs in families.

In addition, smoking is a risk factor that increases the likelihood of developing this vascular disease. It has also been found that individuals who already suffer from various connective tissue disorders have an increased risk of developing fibromuscular dysplasia. These disorders include:

• Ehlers-Danlos syndrome type 4
• Neurofibromatosis
• hereditary nephritis (also known as Alport syndrome) and
• cystic median necrosis

The condition is more common in women between the ages of 30 and 50. Therefore, researchers believe that hormonal factors also play a role in fibromuscular dysplasia. However, the disease can occur at any age and in both sexes.

Fibromuscular dysplasia is generally diagnosed using vascular imaging.

One of these methods is duplex sonography, a specialized technique within the field of ultrasound imaging (sonography). This allows the physician to measure and visualize blood flow, thereby detecting abnormalities. It does not involve radiation and is therefore suitable for everyone.

Narrowing of the blood vessels can also be visualized using computed tomographic angiography (CTA). This technique can also visualize veins and arteries. Magnetic resonance angiography (MRA) is another imaging technique that can be used in this context.

Both procedures help detect narrowing of blood vessels. Digital subtraction angiography (DSA) provides a particularly precise diagnosis. This procedure uses a catheter. To perform it, the doctor makes a small incision in the femoral artery and advances a guidewire with the catheter to the site of the stenosis. DSA is generally used only when the narrowing of the blood vessel needs to be corrected, for example, through balloon dilation.

Treatment for fibromuscular dysplasia generally targets the symptoms the patient is experiencing. It also depends on the exact location of the vascular abnormality. If there are no symptoms, treatment is not necessary. However, lifelong monitoring should be conducted. 

Medication for fibromuscular dysplasia may be used depending on the type and severity of the symptoms. If, for example, the carotid arteries are affected, there may be a risk of embolism. In that case, the treating physician will prescribe antiplatelet medications. These medications are intended to prevent blood platelets from clumping together. A well-known active ingredient in this class is aspirin (ASA).

If symptoms occur, angioplasty may be an option in select cases. During this procedure, the doctor attempts to widen the affected vessel using balloon dilatation. The physician uses a balloon catheter to expand the artery. The placement of a stent—an implant designed to keep the blood vessel open—is usually not necessary.

Balloon dilation can increase the cross-sectional area of the vessel (shown here in a case of atherosclerosis with a stent) © phonlamaiphoto | AdobeStock

If neither medication nor balloon dilation produces the desired results, surgery may be necessary. In this procedure, the affected segment of the blood vessel is removed and replaced, usually with the patient’s own tissue. These surgeries should be performed by an experienced vascular surgeon.

Medical specialists in vascular diseases such as fibromuscular dysplasia are vascular specialists. These include vascular surgeons and angiologists.

Vascular surgery is a distinct branch of surgery, while angiology is a subspecialty of internal medicine.

In many cases, fibromuscular dysplasia is asymptomatic. Therefore, regular monitoring of the condition is usually sufficient to detect any changes in a timely manner.

Patients diagnosed with a vascular disease such as fibromuscular dysplasia should stop smoking immediately. It is also recommended that they have other risk factors checked regularly by a doctor. This is to rule out

• high or low blood pressure is present, and to
• there are lipid metabolism disorders or
• diabetes mellitus.

These may have a negative impact on the course of the disease.

If further measures are necessary, they generally have a positive effect on symptoms. In such cases, a consultation with an experienced vascular specialist is required.

What is fibromuscular dysplasia?
Fibromuscular dysplasia is a non-inflammatory vascular disease affecting medium-sized arteries. Thickening and fibrosis of the arterial wall lead to narrowing or stenosis, which can impair blood flow.

What symptoms does FMD cause?
The signs and symptoms depend on which vessels are affected. Many patients suffer from hypertension, dizziness, headaches, or reduced blood flow. If the carotid arteries or coronary arteries are affected, neurological symptoms or angina may occur.

How is fibromuscular dysplasia diagnosed?
Fibromuscular dysplasia is usually diagnosed using angiography, magnetic resonance angiography, or subtraction angiography. Multifocal and string-of-pearls-like changes in the arteries are typical. In addition, stenosis or aneurysms in the renal artery may be detected.

What is the treatment for fibromuscular dysplasia?
Treatment for fibromuscular dysplasia depends on the severity of the condition. For symptomatic patients, angioplasty, stenting, or antiplatelet therapy may be considered. In addition, controlling high blood pressure and quitting smoking are important for preventing cardiovascular disease.

What are the causes and risk factors?
The exact cause is unclear. Genetic changes, connective tissue disorders, and hormonal influences are among the factors under discussion. Smoking is considered a major risk factor for the development of fibromuscular dysplasia and other vascular diseases such as arteriosclerosis or atherosclerosis.