What Is Fibromuscular Dysplasia?

Fibromuscular dysplasia (FMD) is a rare arterial disorder in which the cells in the walls of the arteries are replaced with weaker, less flexible fibrous cells. FMD results in stiff and damage-prone arterial walls, causing narrowing, weakening, and tearing of arteries.

This article will explain the types of fibromuscular dysplasia, its causes, diagnosis, and treatment.

Types of Fibromuscular Dysplasia

FMD is classified into two main categories based on the appearance of the arteries during diagnostic testing, including:

• Multifocal FMD: The more common form that presents with a string-of-beads pattern a repeated pattern of bulging and narrowing of the artery
• Focal FMD: The less common form that presents as a single focal area with narrowing or bulging of the artery

FMD most commonly involves the arteries in the following areas:

• Neck and brain (carotid and vertebral arteries)
• Kidneys (renal arteries)
• Stomach organs and bowels (mesenteric arteries)
• Arms (brachial arteries)
• Legs (iliac arteries)
  

FMD usually affects middle-aged women, but can affect men and children as well.

Fibromuscular Dysplasia Symptoms

FMD symptoms depend on the location of the arteries and the extent of the narrowing or bulging in the area. Symptoms and pain caused by FMD usually derive from the organ that is supplied by the FMD-affected artery.

For example, if the arteries in the kidney are affected, symptoms may include:

• Poor kidney function
• High blood pressure (hypertension)

FMD caused by the carotid or vertebral arteries that supply the neck and brain may cause symptoms such as:

• Neurological symptoms involving facial nerves, such as drooping eyelids, or unequal pupils
• Headaches
• A swooshing sound in the ears
• Dizziness
• Stroke
• Sudden neck pain
• Transient ischemic attack (TIA), or ministroke
• Intracranial aneurysm (a bulge in a blood vessel in the brain)
• Intracranial hemorrhage (bleeding in the brain)

FMD symptoms caused by the mesentery arteries that supply the intestines, liver, or spleen may include:

• Unexplained weight loss
• Abdominal pain after eating

FMD symptoms caused by arteries in the arms and legs can cause:

• Arm or leg discomfort with exercise
• Unequal blood pressure readings in the arms

In some cases, people with FMD have no physical symptoms upon examination.

Causes

Unfortunately, little is known about the causes of FMD. However, researchers report that some causes are believed to be genetic, and FMD may be related to certain hormones, as many people diagnosed with FMD are women of childbearing age.

Unlike other, more common arterial diseases, FMD is not caused by:

• A buildup of fats, cholesterol, and other substances (plaque) inside the walls of the artery (atherosclerosis)
• Vessel inflammation (vasculitis)
• Blood clots (thrombus)

The most common arterial wall disease is atherosclerosis, caused by plaque that forms around the insides of the artery that reduces blood flow. FMD is an arterial wall disease that occurs even without any plaque buildup.

Diagnosis

The gold standard for diagnosing FMD is angiography, which is an examination of blood vessels using a catheter, X-ray, imaging to guide placement, and a contrast dye to locate abnormalities. However, other noninvasive imaging may be used, such as:

• Computed tomographic (CT) angiography (using a series of X-ray images and an injectable dye)
• Duplex ultrasound (using high-frequency sound waves)
• Magnetic resonance angiography (MRA; using a powerful magnetic field and radio waves)

A diagnosis may occur when a healthcare provider hears a specific noise over one of the arteries due to disturbed or turbulent blood flow within the vessel. The noise is called a bruit.

Treatment

Unfortunately, there is no cure for FMD. The goal of treatment is to manage FMD symptoms and complications. Treatments may include:

• Antiplatelet medications, such as aspirin, for high blood pressure
• Over-the-counter (OTC) or prescription medication for headaches
• Not smoking, with programs to help quit smoking likely being prescribed to smokers

Sometimes, healthcare providers attempt to improve blood flow through a severely narrowed artery. It depends on the location of the artery and symptom severity. If symptoms are severe, a percutaneous transluminal angioplasty (PTA), or balloon angioplasty (using a balloon to stretch and open up a blocked artery), may be performed.

Prognosis

There is no cure for fibromuscular dysplasia, but there are effective treatments, such as medicines and angioplasty, to reduce the risk of stroke. Many people with FMD go on to have a normal life expectancy.

FMD-related aneurysms may burst and bleed into the brain, causing an intracranial stroke, permanent nerve damage, or death. Fortunately, aneurysms, when caught early, are often treatable.

Summary

Fibromuscular dysplasia is a rare arterial disorder in which the cells in the arterial walls become replaced with weaker, less flexible fibrous cells. This results in stiff, narrow, and damage-prone arterial walls. FMD is found in arteries throughout the body, although it most commonly involves the arteries that lead to the kidneys, neck, brain, legs, arms, and abdominal organs.

The causes of FMD are unknown. However, some cases may be genetic or related to hormones. Diagnosis is essential to ensure FMD symptom management and treatment.