Fibromuscular dysplasia is a vascular disease characterized by abnormal cell growth in the walls of medium and large arteries, leading to a beaded appearance. This can have some negative consequences, causing arteries to become narrower, reducing blood flow, and in some cases, leading to bulging blood vessels (aneurysms) or dissections (artery tears).
The most common arteries involved in fibromuscular dysplasia are the carotid (found on the sides of the neck), vertebral (found at the base of the neck), and the renal arteries of the kidney. Less commonly involved arteries that may be affected by fibromuscular dysplasia include the mesenteric arteries of the intestines, arteries of the arms and legs, and the coronary arteries of the heart.
Women between the ages of 40 and 60 are the most commonly affected by fibromuscular dysplasia (90 percent), but the condition may also occur in children and the elderly. While not a common occurrence in men, when it does present itself in males, a higher risk of an aneurysm or dissections is a result.
Is fibromuscular dysplasia common?
The exact frequency fibromuscular dysplasia in the general population is difficult to determine, but it is considered a relatively uncommon condition. Much of the reason for this uncertainty is because those with mild forms of the disorder are often asymptomatic (without symptoms), going undetected. Most studies on the condition have only looked at specific patient populations who have already suffered from serious consequences of having fibromuscular dysplasia, making estimates of how widespread the condition actually is very difficult.
What are the types of fibromuscular dysplasia?
Classification of fibromuscular dysplasia is generally done according to the layer of the artery affected and by the lesion the patient had. There is no other way to accurately determine which layer a case of fibromuscular dysplasia has affected until it has been examined under a microscope. This means that a biopsy of the affected region needs to be harvested to obtain a truly accurate diagnosis, of which there are five recognized types, but this is rarely done. These five fibromuscular dysplasia types include:
- Medial fibroplasia
- Intimal fibroplasia
- Perimedial fibroplasia
- Medial hyperplasia
- Periarterial hyperplasia
Instead, diagnosis is primarily achieved using imaging studies. This method is more practical and efficient, but it does require the diagnostic criteria for fibromuscular dysplasia to be simplified to only two types to match the appearance of the disorder seen in imaging studies. These fibromuscular dysplasia types include:
Multifocal fibromuscular dysplasia:
- The most common type affecting about 90 percent of patients with fibromuscular dysplasia
- Patients commonly present with the “beads on a string” appearance, caused by alternating areas of widening and narrowing of the artery in question
- Includes medial fibroplasia (most common multifocal type) and perimedial fibroplasia types
Focal fibromuscular dysplasia:
- The least common type affecting less than 10 percent of patients with fibromuscular dysplasia
- Patients often present with distinct focal lesions or tubular narrowing
- Includes intimal fibroplasia (most common focal type), periarterial fibroplasia, and medial hyperplasia types
Causes, risk factors, and complications of fibromuscular dysplasia
The cause of fibromuscular dysplasia is unknown, but the following are believed to play significant roles in its development:
- Genetics: Considered a loose association, as it is not clear whether genetics plays a true role in the development of fibromuscular dysplasia. Having a close family member with the condition does not mean you will also develop it. Additionally, not every patient with fibromuscular dysplasia has a family member also with the disease.
- Hormones: This is believed to have some correlation with the development of fibromuscular dysplasia, due to the fact that the condition occurs more commonly in women than it does men. However, the condition is not linked to other times of increased female hormone, as in the case of pregnancy and when using the birth control pill.
- Abnormally formed arteries: Possibly caused by inadequate positioning of arteries in the body, leading to poor delivery of oxygenated blood to the arteries that supply blood vessel wall. Abnormally formed arteries can lead to the creation of cells clusters within the artery wall, possibly causing it to become narrow and reduce blood flow.
Risk factors that may promote the development of fibromuscular dysplasia include:
- Sex: Being female
- Age: The condition is more commonly diagnosed in those in their early 50s
- Smoking: Those who smoke are considered at greater risk of developing fibromuscular dysplasia. Additionally, those already with the disease who smoke are at risk of making the disease more serious.
Some of the most commonly recognized complications of fibromuscular dysplasia include:
- High blood pressure: The narrowing of arteries leads to higher pressure on arterial walls, which can lead to artery damage, heart disease, or even heart failure.
- Dissected artery: Also known as arterial dissection or spontaneous coronary artery dissection (SCAD) causing blood to leak into the arterial wall, limiting blood flow to organ or tissue supplied by the affected artery.
- Aneurysms: Caused by weakening of the artery walls, creating a bulge with the potential for rupture. When a rupture occurs, it can be life-threatening.
- Stroke: Arterial dissection leading to the brain or having a brain aneurysm that ruptures can lead to a stroke. Having high blood pressure is also a risk factor for stroke development.
What are the symptoms of fibromuscular dysplasia?
Signs and symptoms of fibromuscular dysplasia will depend on the particular artery affected by the disease. However, it is important to note that some individuals with mild forms of the condition may not present with symptoms at all. Fibromuscular dysplasia symptoms may include:
When affecting the arteries of the kidney:
- High blood pressure
- Kidney tissue damage
- Chronic kidney failure (rare)
When affecting arteries leading to the brain (carotid arteries):
- Blurred vision or temporary vision loss
- Ringing in the ears (tinnitus)
- Facial weakness or numbness
When affecting abdominal arteries (mesenteric arteries):
- Abdominal pain after meals
- Unintentional weight loss
When affecting arteries leading to the arms or legs (peripheral arteries):
- Cold limbs
- Appearance or color changes of the skin
- Discomfort when moving the arms, legs, hands, or feet
When affecting the arteries leading to the heart (coronary arteries):
How to diagnose fibromuscular dysplasia
When presented with a potential case of fibromuscular dysplasia, your doctor will want to rule out another cause of narrowed blood vessels known as atherosclerosis. This will involve a physical exam and obtaining blood values for blood sugar and cholesterol levels. However, atherosclerosis tends to present itself in certain demographics, and its presentation in younger adults is out of place. This will often lead to further investigation using imaging tests that may include the following, looking for the hallmark “beads on a string” appearance.
- Catheter-based angiography: Using a catheter (a thin tube) that is inserted into one of the arteries and moved to the affected region. A small amount of contrast dye is then used and an x-ray image is taken to get a good picture of the blood vessel and its structure. This is a commonly used test for fibromuscular dysplasia.
- Doppler ultrasound: A non-invasive test that uses sound waves to produce images on a monitor of various internal bodily structures. It can be used to show how fast your blood is flowing as well as the size and shape of blood vessels.
- Computerized tomography (CT) angiogram: A detailed imaging study that allows your doctor to check if arteries are narrowed or blocked. This test requires the use of contrast dye to help make the obtained image stand out once taken.
- Magnetic resonance imaging (MRI): Using a magnetic felid and radio waves to capture images of internal structures, MRIs can provide some of the most detailed images of blood vessels and soft tissue.
What are the treatment options for fibromuscular dysplasia?
Treatment options for fibromuscular dysplasia will be different from patient to patient, often depending on overall patient health, any underlying conditions (such as high blood pressure), as well as the location of the narrowed artery.
If otherwise healthy, repair of the affected artery is often recommended using various medical procedures and/or surgery. These may include:
- Percutaneous transluminal angioplasty (PTA): Often performed simultaneously with a catheter-based angiogram, as access to the affected region is required. Once the angiogram has been completed, a wire is threaded through the catheter with an attached balloon. This balloon is then inflated to open up the narrowed artery.
- Surgical revascularization: This more invasive procedure is performed when a PTA is not an option and the narrowing of the artery is severe. The surgery will typically involve the replacement of the affected artery by another one harvested from elsewhere in the body. A type of revascularization surgery is an aortorenal bypass, which replaces the artery that leads to the kidney from one taken from the leg.
The use of several types of blood pressure-reducing medications is often recommended for fibromuscular dysplasia patients. Lowering blood pressure using drugs is still recommended even after doctors have already performed procedures correcting the condition. The following are some drugs used in fibromuscular dysplasia treatment:
- Angiotensin-converting enzyme (ACE) inhibitors: Includes medication like benazepril (Lotensin), enalapril (Vasotec), or lisinopril (Prinivil, Zestril) which help to stop narrowing of the blood vessels.
- Angiotensin II receptor blockers: Includes medication like candesartan (Atacand), irbesartan (Avapro), losartan (Cozaar), and valsartan (Diovan), which help relax blood vessels.
- Diuretics: Act to remove excess fluid from the body to reduce blood pressure. Hydrochlorothiazide is one of the most common diuretics used for blood pressure management
- Calcium channel blockers: Includes amlodipine (Norvasc) and nifedipine (Adalat CC, Afeditab CR, Procardia), which help relax blood vessels.
- Beta blockers: Help to slow heart rate and block adrenaline. Medications in this class include metoprolol (Lopressor, Toprol-XL) and atenolol (Tenormin).
- Aspirin: May be offered to reduce the incidence of stroke.
Activity to follow for fibromuscular dysplasia patients
Fibromuscular dysplasia patients are often advised accordingly based on their own unique presentation. For example, if cerebral aneurysms exist, strenuous activity should be avoided, as this may increase blood pressure. Additionally, all smokers are advised to quit as the habit can make fibromuscular dysplasia worse.