Fibromuscular dysplasia (FMD) is a rare blood vessel disorder characterized by abnormal fibrous cell growth in the walls of medium- and large-sized arteries, causing them to stiffen and weaken. This can lead to arterial narrowing (stenosis), reducing blood flow to vital organs and increasing the risk of serious complications, such as aneurysms. Unlike atherosclerosis and many other vascular conditions, FMD is not caused by blood vessel inflammation or plaque buildup.

Usually, fibromuscular disease affects the renal arteries in the abdomen, which lead to the kidneys, and the carotid and vertebral arteries in the neck, which lead to the brain. Much less frequently, it affects the mesenteric arteries in the midsection, which lead to the digestive tract, and the brachial and iliac arteries that supply blood to the arms and legs.

Although fibromuscular dysplasia is uncommon, its incidence is more discoverable than ever before. Many experts attribute this trend to ongoing advancements in medical imaging, which have led to increased diagnoses, particularly in women. Understanding FMD can lead to early detection and appropriate management, which are essential for maintaining optimal heart health.

What Are the Types of Fibromuscular Dysplasia?

Fibromuscular disease is classified based on the pattern of arterial involvement when viewed in medical images, such as an angiogram. The two main types are:

• Multifocal FMD – Multiple areas of abnormal tissue growth cause alternating sections of narrowing and dilation in the affected arteries, creating a distinctive “string of pearls” appearance.
• Unifocal FMD – Less common and typically more aggressive than multifocal FMD, unifocal FMD presents as a single, well-defined narrowing in an artery. Exceedingly rare in adults, the condition primarily affects children and may require intervention, such as angioplasty or surgery.

What Causes Fibromuscular Dysplasia and What Are the Risk Factors?

The exact cause of fibromuscular disease is not well understood. Researchers believe it likely results from a combination of factors, which may include:

• Genetics – FMD appears to run in families, suggesting a hereditary component, and although no specific gene has been identified, some studies have linked genetic variants such as PHACTR1 to the condition.
• Hormones – Because fibromuscular dysplasia predominantly affects women of childbearing age, scientists believe hormonal fluctuations may play a role in its development, although no direct hormonal link has been established.
• Mechanical stress – Repeated movements or trauma may weaken the walls of the arteries, making them more prone to damage.
• Vascular abnormalities – Fibromuscular disease may be related to irregular arterial development before birth.

Certain factors may increase the likelihood of developing FMD. These include:

• Age – Although fibromuscular dysplasia can occur at any age, multifocal FMD is most often diagnosed in middle-aged adults, while unifocal FMD mainly affects children.
• Gender – For unknown reasons, women are significantly more likely to develop fibromuscular disease than men.
• Genetics – A family history of FMD or other vascular conditions may increase the risk.
• High blood pressure – Chronic hypertension is commonly associated with fibromuscular dysplasia and may contribute to its development.
• Smoking – Tobacco use may contribute to FMD progression and worsen its symptoms.

What Are the Warning Signs and Symptoms of Fibromuscular Dysplasia?

In some cases, fibromuscular disease does not cause symptoms and is detected through an imaging test performed for an unrelated reason. When noticeable symptoms occur, they can vary depending on the severity of the condition and which arteries are affected, such as:

• Carotid and vertebral arteries – Symptoms can include headaches (migraine or nonmigraine), dizziness, ringing or whooshing sounds in the ears (pulsatile tinnitus), neck pain and vision problems. Additionally, if blood flow to the brain is disrupted, a transient ischemic attack (TIA) or stroke may occur.
• Coronary arteries – Common warning signs include chest pain and shortness of breath. If blood supply to the heart is significantly reduced, a heart attack may occur.
• Peripheral arteries – Pain, numbness and weakness in the limbs may develop due to reduced blood flow, especially with exertion.
• Renal arteries – The most common symptom is hypertension; in severe cases, reduced blood flow to the kidneys may lead to kidney damage or failure.

If left untreated, fibromuscular dysplasia can lead to life-threatening complications that warrant emergency medical attention. Warning signs that should be heeded include:

• Heart attack – Rapid-onset chest pain and shortness of breath
• Narrowing of the carotid arteries in the neck – Pulsatile tinnitus
• Narrowing of the renal arteries – Abrupt spike in high blood pressure (hypertensive crisis) that does not respond to treatment
• Stroke – Sudden severe headache, confusion or weakness

How Is Fibromuscular Dysplasia Diagnosed?

The diagnostic process for fibromuscular disease typically involves a combination of clinical evaluation and imaging tests. Because FMD can affect different arteries and mimic other vascular conditions, a thorough assessment is essential to ensure an accurate diagnosis.

Medical History and Physical Examination

After reviewing the patient’s symptoms, medical history and risk factors, the physician will usually perform a physical exam to check for:

• High blood pressure, which is common in renal artery FMD
• Whooshing sounds (bruits) that can be heard through a stethoscope placed over the abdomen or neck, suggesting turbulent blood flow
• Neurological symptoms, such as vision changes and dizziness, which may indicate carotid or vertebral artery involvement

Imaging Tests

Imaging plays a key role in diagnosing fibromuscular dysplasia, allowing the physician to visualize the structure of the arteries and identify abnormalities, such as narrowing, blockages and aneurysms, as well as the characteristic bead-like pattern of multifocal FMD. Common imaging techniques include:

• Computed tomography angiography (CTA) – Uses X-rays and contrast dye to create three-dimensional (3D) images of blood vessels
• Magnetic resonance angiography (MRA) – Uses magnetic fields and contrast dye to create comprehensive visuals of arteries
• Catheter-based angiography – Uses contrast dye injected directly into the arteries to create highly detailed X-ray images of blood vessels
• Doppler ultrasound – Uses sound waves to evaluate blood flow through certain arteries, particularly those supplying the brain or kidneys

Additional Diagnostic Tests

If hypertension is present, the physician may order further testing to evaluate kidney function. Additionally, the physician may suggest genetic testing if the patient has a family history of FMD or other vascular conditions.

How Is Fibromuscular Dysplasia Treated?

FMD treatment requires a multidisciplinary approach that focuses on managing symptoms, preventing complications and improving blood flow to the affected areas of the body. The specifics can vary based on the arteries involved, the severity of the condition and the presence of complications. Options may include:

Medications

If the patient has hypertension—particularly if the renal arteries are affected by FMD—the physician may prescribe angiotensin-converting enzyme (ACE) inhibitors, angiotensin II receptor blockers (ARBs) or calcium channel blockers to control blood pressure. Additionally, if blood clots have formed, the physician may prescribe antiplatelet or anticoagulant therapy (blood thinners) to reduce the risk of stroke.

Interventional Procedures

To address renal or carotid artery involvement, the physician may suggest angioplasty. After inserting a small balloon-like device into a narrowed artery, the physician will inflate the balloon to widen the artery and improve blood flow. After angioplasty, the physician may place a mesh tube (stent) inside the widened artery to keep it open and prevent artery restenosis. If FMD causes severe arterial damage or aneurysms, surgical repair or bypass may be necessary to restore normal blood flow.

Lifestyle Modifications

Many patients with fibromuscular dysplasia and other vascular conditions benefit greatly from:

• Healthy eating – A balanced diet low in salt, fats and cholesterol can help manage blood pressure and reduce cardiovascular risks.
• Regular exercise – Low-impact, physician-recommended activities can improve cardiovascular health and help prevent complications.
• Smoking cessation – Quitting smoking is a critical aspect of treatment; tobacco use can worsen the condition and increase the likelihood of complications.

Ongoing Monitoring and Follow-Up

Regular monitoring with imaging studies, such as CTA, MRA or ultrasound, is essential to track the progression of fibromuscular dysplasia, evaluate blood flow and identify new complications or further narrowing of the arteries.

What Are the Possible Complications and Long-Term Effects of Fibromuscular Dysplasia?

While fibromuscular disease can often be managed with treatment, the condition can have several complications and long-term effects. These include:

• Aneurysms – FMD can weaken the arterial walls, increasing the risk of aneurysms. If a bulging aneurysm ruptures, it can cause life-threatening internal bleeding or organ damage, requiring immediate medical intervention.
• Arterial dissection – In rare cases, fibromuscular dysplasia may cause an artery to tear or dissect, disrupting normal blood flow and leading to serious complications, such as stroke and organ damage.
• Hypertension – Fibromuscular disease often affects the renal arteries, which can cause kidney dysfunction and secondary high blood pressure. Uncontrolled hypertension can damage the heart, kidneys and other organs, potentially resulting in cardiovascular disease or kidney failure.
• Organ damage – If FMD affects major arteries that supply vital organs, reduced blood flow can damage those organs. For instance, if left untreated, impaired renal artery function can cause chronic kidney disease or kidney failure.
• Nonatherosclerotic peripheral artery disease (PAD) – Fibromuscular dysplasia can reduce blood flow to the arms and legs, leading to pain, cramping and, in severe cases, tissue damage that requires amputation.
• Recurrence or disease progression – Even after treatment, fibromuscular disease may progress, and its symptoms may recur. For example, arterial restenosis can develop after angioplasty, requiring ongoing monitoring and possibly additional interventions.
• Transient ischemic attack and stroke – If fibromuscular dysplasia affects the carotid or vertebral arteries, it may reduce blood flow to the brain, increasing the risk of a TIA or stroke. A TIA may serve as a critical warning sign of an impending stroke, which can result in permanent neurological damage.

How Can Fibromuscular Dysplasia Be Prevented?

Fibromuscular disease cannot be completely prevented, mainly because its exact cause remains unknown. Additionally, scientists believe the condition may have a genetic component. Even so, certain steps can be taken to manage it and help reduce the risk of complications. These include:

• Exercising regularly – Low-impact physical activities, such as walking and swimming, can improve cardiovascular health and help keep blood pressure in check.
• Maintaining healthy eating habits – A balanced, heart-healthy diet low in sodium and saturated fats can help control blood pressure and promote overall wellness.
• Managing hypertension – High blood pressure is a common complication of FMD, particularly when the renal arteries are affected. Regular monitoring and prescribed medications can help prevent damage to vital organs and reduce the risk of heart disease and stroke.
• Quitting smoking – Tobacco use can worsen fibromuscular dysplasia and other vascular conditions; therefore, smoking cessation is a key preventive measure.
• Seeking genetic counseling – Individuals with a family history of fibromuscular disease may benefit from genetic counseling, which can help assess their own risk level and determine whether any relatives should consider early screening or monitoring.

Living With Fibromuscular Dysplasia

Life with fibromuscular disease can vary from patient to patient depending on the severity of the condition, the arteries affected and the presence of complications. While some individuals may experience few or no symptoms, others might require ongoing medical management to control hypertension, prevent stroke or address vascular complications.

With appropriate medical care, however, many people with fibromuscular dysplasia can lead a normal, active life. Nevertheless, some FMD-related challenges may persist, such as:

• Fatigue and headaches – Carotid artery involvement may cause headaches, dizziness or ringing in the ears, which can impact daily activities.
• Hypertension – If the renal arteries are affected, blood pressure control with medication and lifestyle changes is often necessary.
• Pain or discomfort – Due to reduced blood flow, some patients may experience neck, abdominal or limb pain.

Additionally, fibromuscular dysplasia is a chronic medical condition that can cause stress and anxiety, especially for those at heightened risk of serious complications, such as stroke and aneurysms. Some people may find it helpful to seek support from:

• Mental health professionals – Counseling or therapy can help a patient cope with the uncertainties of living with a vascular disorder.
• Peer groups – By connecting with others facing similar challenges, a patient can benefit from both practical advice and emotional support.

Because fibromuscular disease can progress over time, regular follow-up appointments and imaging tests are often needed to monitor blood vessel health and detect any new complications early.

Benefit From World-Class Care at TGH

Tampa General Hospital is nationally recognized for providing advanced, comprehensive care for patients with vascular disease, including fibromuscular dysplasia and other rare and complex conditions. We are proud to be the only hospital in the Tampa Bay area to be included in the list of “100 Hospitals and Health Systems with Great Heart Programs” compiled by Becker’s Hospital Review. In addition, U.S. News & World Report named us One of the Nation's Best Hospitals for Heart & Vascular Care and recognized us as a High Performing Hospital for Heart Attack and Heart Failure treatment for 2024-25.

If you would like to learn more about FMD, contact us at (813) 844-3900 to request an appointment with an expert in our nationally recognized Heart and Vascular Institute or email heart-vascular@tgh.org.