Fibromuscular Dysplasia

What is Fibromuscular Dysplasia?

Fibromuscular Dysplasia (FMD) is a health condition characterized by narrowing of arteries. It affects those arteries which have an abnormal growth of cells or fibrous tissue on their walls. This causes stenosis or narrowing of the arteries involved, which can lead to damaging of the organs that are supplied blood through the constricted artery.

FMD mostly affects the arteries that lead to kidneys, but may also affect the arteries which lead to the brain, the arms and legs and the abdomen.

Fibromuscular Dysplasia ICD-9 Codes

The ICD-9 codes for Fibromuscular Dysplasia are listed below.

• 447.3
• 447.8

Fibromuscular Dysplasia Types

There are five different types of FMD, categorized on the basis of the portion of the arterial wall that is affected as well as the associated characteristics of the dysplasia.

Picture 1 – Fibromuscular Dysplasia

Medial fibroplasia

• Nearly 75% to 80% of all cases of Fibromuscular Dysplasia are of this type.
• It affects the middle layer of the artery wall, known as tunica media.
• It is characterized by presence of fibrous lesions that are alternated by aneurysms or bulging areas.
• Has a string of beads-like appearance on dye angiogram.
• Percentage of this form of dysplasia is low, occurring in less than 10% of all Fibromuscular Dysplasia cases.
• It is caused by deposits of collagen or fibrous tissue around tunica intima, the arterial wall’s inside layer.
• A dye angiogram shows a concentric, smooth narrowing appearance sans any beading.
• Like the intimal type, Perimedial fibroplasia occurs in less than 10% of cases.
• Extensive amounts of collagen are deposited around the outer portion of tunica media.
• Arterial walls become irregularly thickened.
• Has got a string of beads-like appearance but unlike medial fibroplasia, the beads have a smaller diameter than a normal artery.
• The potential for total blocking of the affected arteries is increased.
• Only 1% to 2% of FMD cases are of this type.
• It is caused by a surplus formation of the smooth muscle cells.
• There is an absence of fibrous deposits.
• On angiogram, it takes an appearance similar to that of intimal fibroplasias.
• It is the rarest form of dysplasia, occurring in less than 1% of all cases.
• Expansion of adventitia leads to Periarterial hyperplasia.
• The collagen extends to the fat layers surrounding adventitia.
• Inflammations of the artery as well as that of the surrounding area are the principal characteristics of this form of Periarterial hyperplasia.

Intimal fibroplasia

Perimedial fibroplasia

Medial hyperplasia

Periarterial hyperplasia

Fibromuscular Dysplasia Causes

Although the exact causes responsible for FMD are not known, it is believed that various factors may trigger the symptoms of this disorder. These include:

Genetics

Fibromuscular Dysplasia is inherited in an autosomal dominant pattern. The genes of an individual are believed to play a major part in the development of this disorder. However, even if a person has a family member or relative who has Fibromuscular Dysplasia, it does not mean that that person will be affected by the disorder. The individual may also develop the condition in another artery; the disease may also differ in degree of intensity in his or her case. Apart from this, not every patient affected by Fibromuscular Dysplasia has got a family member or relative affected by the disease. Other types of genetic disorders that affect blood vessels may also lead to FMD.

Hormones

As premenopausal women are affected by FMD more frequently than men, it is believed that hormones may play a role in the development of this disease. However there are no connections between FMD and a woman’s history of pregnancy.

Abnormal formation of arteries

The blood vessels take an abnormal shape if the arteries which supply blood to the blood vessel walls are not supplied with enough oxygen. This might lead to FMD. FMD can also occur if the placement of the arteries in one’s body is not normal, or if the arteries develop abnormally due to some medication or tobacco. Abnormal development of arteries leads to formation of cell clusters or fibrous lesions in artery walls, which narrows the arteries and reduces flow of blood.

Fibromuscular Dysplasia Risk Factors

Numerous factors can increase the chances of developing this disorder or aggravate existing symptoms. These are discussed below:

Sex

Women are more prone to this disorder than men.

Age

FMD occurs more frequently in people between the ages of 25 and 50 years.

Smoking

Individuals who smoke tend to be more affected by FMD than nonsmokers. Smoking can aggravate the already existing symptoms of this disease in case of people who have been diagnosed with FMD.

Fibromuscular Dysplasia Symptoms

A lot of people having FMD do not experience any symptoms. Others have symptoms depending on the level of damage sustained by the arteries and the extent of stenosis. The symptoms also depend on what type of arteries is being affected, with each showing slightly different signs.

Symptoms for Kidney or Renal artery

These include:

• High blood pressure or renovascular hypertension
• Diminished kidney function or renal insufficiency
• Ischemic renal atrophy or damage of tissues in the kidney
• In some very rare cases, chronic kidney failure

Symptoms for Carotid or Vertebral artery

These involve:

• Dizziness
• Neck pain
• Carotid dissection
• Chronic headaches
• Hemorrhagic stroke
• Facial numbness or weakness
• Temporary vision loss or blurred vision
• Tinnitus or ringing sensation in the ears

Symptoms for Mesenteric or Abdominal artery

These involve:

• Unintended weight loss
• Abdominal pain and discomfort after eating

Symptoms for Peripheral arteries or arteries of arms and legs

These include:

• Cold limbs
• Weakness of arms and legs
• Numbness of arms and legs
• Skin becomes different in color and appearance
• Discomfort while moving arms, legs, hands and feet

Advanced cases of FMD might include symptoms such as transient ischemic attacks, strokes and heart attacks.

Fibromuscular Dysplasia Prevention

There are no known ways to prevent FMD. However, if an individual is a smoker, he or she can quit smoking which can reduce the risk of development of this disorder.

Fibromuscular Dysplasia Diagnosis

Fibromuscular Dysplasia is frequently diagnosed when an individual is going through a scan or an X-ray for some other health problem. In some other cases, the doctor may diagnose a patient with FMD while conducting a routine physical checkup if he or she hears a swishing noise in the abdomen or neck area that indicates abnormality of blood flow. Once a patient is diagnosed with Fibromuscular Dysplasia in one area of the body, the other blood vessels of the body are also evaluated to check for further arterial blockage. Fibromuscular Dysplasia can be diagnosed by conducting non-invasive imaging studies such as MRA or magnetic resonance angiography, CTA or computed tomography angiography and duplex ultrasound. These tests allow determining the extent and intensity of the lesions. Occasionally the patient may have to go through a dye angiogram test, a standard for the diagnosis of Fibromuscular Dysplasia. Dye angiogram studies are generally conducted when other tests for FMD do not produce satisfactory results or when a patient requires undergoing therapeutic procedures like balloon angioplasty. Catheter-based angiography is another imaging technique that produces accurate images of the arteries. Other important tests for diagnosing Fibromuscular Dysplasia include Digital Subtraction Angiogram test, Magnetic resonance imaging and Doppler ultrasound test.

Fibromuscular Dysplasia Differential Diagnosis

The differential diagnosis for FMD includes isolating its symptoms from those of conditions like:

• Atherosclerotic stenosis
• Stenosis linked with type 1 neurofibromatosis
• Vascular Ehlers-Danlos syndrome
• Williams’ syndrome

Fibromuscular Dysplasia Treatment

The treatment for FMD is based on the overall health of the patient, location of the stenosis-affected artery as well as other underlying conditions the patient may have, like high blood pressure. The treatment options include medications, medical procedures and surgery.

Medications

People with this disorder are often treated with medications that belong to different categories. These categories are described below:

Angiotensin II receptor blockers

These help in relaxing the blood vessels by preventing the actions of a chemical that narrows the blood vessels. Medications of this type include irbesartan (Avapro), candesartan (Atacand), valsartan (Diovan) and losartan (Cozaar).

Angiotensin-converting enzyme inhibitors (ACE)

These involve medications such as enalapril (Vasotec), benazepril (Lotensin), lisinopril (Zestril, Prinivil), prevents narrowing of the blood vessels.

Diuretics

Diuretics like hydrochlorothiazide (Microzide) help in removing excess from the patient’s body and can be used along with other medications for treating blood pressure.

Beta blockers

Beta blockers like metoprolol (Toprol-XL, Lopressor) and atenolol (Tenormin) help in slowing the heartbeat and blocks adrenaline.

Calcium channel blockers (CCB)

CCBs like nifedipine (Procardia, Adalat) and amlodipine (Norvasc) help in relaxing the blood vessels.

Surgical and Medical Procedures

FMD is also often treated by curing the affected artery and improving blood flow. This can be done by the following procedures.

Percutaneous transluminal renal angioplasty (PTRA)

In this procedure, a balloon-mounted catheter is placed inside the narrowed or blocked region of the artery. The catheter is then moved through blood vessel by using a unique X-ray machine. Inflating the balloon allows reopening the blood vessel after which the catheter and the balloon are withdrawn.

Stent insertion

Unlike in an angioplasty procedure performed for treating heart disease, placing a stent or a metal mesh tube is not generally required for keeping the artery open. In case of renal arteries, stents should be used only when angioplasty alone is not able to produce satisfactory results. Angioplasty is also recommended for patients having FMD of the carotid arteries.

Surgical Revascularization

In case of severe and complex FMD, surgical revascularization is done to repair the affected area of the artery. The surgical procedure that a particular patient will need depends on the location of the affected artery as well as the extent of the damage. The procedure requires general anesthesia and the patient remains unconscious during the duration of the surgery.

Treatment of Risk Factors

The various risk factors for arterial diseases such as diabetes, high blood pressure, high cholesterol need to be evaluated and treated, especially when signs of aneurysm or dissection are present.

Fibromuscular Dysplasia Follow-Up

Depending on the various clinical signs and symptoms like high blood pressure and headaches, individuals diagnosed with FMD of the renal artery are required to undergo imaging study to evaluate involvement of carotid arteries. Patients having carotid artery FMD should go through imaging studies like magnetic resonance angiography to rule out the possibility of brain aneurysms. Regular clinical check-ups of FMD patients help control the symptoms of the disorder as well as monitor blood pressure. Periodic imaging studies help to evaluate the progression of the disease.

Fibromuscular Dysplasia Complications

FMD may lead to numerous complications, such as:

Picture 2 – Fibromuscular Dysplasia Image

• High blood pressure
• Stroke
• Hypertension
• Heart attack
• Arterial dissection and aneurysm or swelling

Fibromuscular Dysplasia Prognosis

At present there are no definite cures for FMD. The prognosis for the disorder depends primarily on the intensity of the symptoms and the complications that develop. The angioplasty and medicines can reduce the possibility of initial or recurrent strokes. Although doctors can successfully diminish the effect of the symptoms in many cases, severe cases of this type of Dysplasia may lead to permanent nerve damage, bleeding in the brain or even death.

Fibromuscular Dysplasia Prevalence

A few thousand instances of FMD have been reported in the US. However some experts are of the opinion that it affects nearly 5% of the total population. In around 4% of cases, apparently healthy kidney donors were found to be affected by FMD when they were screened with X-rays.

Even though specific data on racial predilection to FMD were unavailable, it is believed that white people tend to be more frequently affected than the black people. Women are found to be more affected than men. The mean age for getting affected by FMD is 48 years and the range lies between 24 years to 70 years of age.

Fibromuscular Dysplasia is a fatal disease. Although it cannot be cured, proper treatment can allow the patient to deal with the disorder effectively. In many instances, the symptoms of this condition can be kept in control with proper medical attention and patients can enjoy a normal healthy life.