What is Fibromuscular Dysplasia (FMD)?

The word “dysplasia” simply means abnormal cellular development or growth. In people with FMD, the dysplasia involves the walls of one or more arteries in the body.  Areas of narrowing, called stenosis, may occur as a result of abnormal cell development.  If enough narrowing causes a decrease in blood flow through the artery, symptoms may result.  Many people with FMD do not have any symptoms or signs on physical examination and are diagnosed by accident during a radiology scan for another problem.

 FMD is most commonly found in the arteries that supply the kidneys with blood (renal arteries).  Up to 75% of all patients with FMD will have disease in the renal arteries. The second most common artery affected is the carotid artery, which is found in the neck and supplies the brain with blood.  Less commonly, FMD affects the arteries in the abdomen (supplying the liver, spleen and intestines) and extremities (legs and arms).  More than one artery may have evidence of FMD in 28% of people with this disease.  

 What causes FMD?

 The cause of FMD is not yet known, but several theories have been suggested.  A number of case reports in the literature have identified the disease in multiple members of the same family including twins.  There is a very strong likelihood that there is a genetic basis for the development of FMD.   However, a relative may have different artery involvement, different disease severity, or not develop FMD at all.  In fact, not all individuals with FMD have a family member with the disease.  In a series from France, about 11% of family members had FMD.

  FMD is also more commonly seen in women than in men resulting in the theory that hormones may play an important role in disease development.  This theory is further supported by the fact that most women are premenopausal at the time of diagnosis.  However, with better imaging available, an increasing number of patients are now being diagnosed later in life. In small population studies, one?s reproductive history (the number of pregnancies and when they occurred) as well as the use of birth control pills did not correlate with the development of FMD.

 Other possible causes of FMD include abnormal development of the arteries that supply the vessel wall with blood resulting in inadequate oxygen supply; the anatomic position of the artery within the body; and tobacco use.  It is likely that many factors are involved in the development of FMD.  This area requires further research.  

 What are the signs and/or symptoms of FMD?

 Many people with this disease do not have symptoms or findings on a physical examination. The signs and/or symptoms that a person with FMD may experience depend on the arteries affected and the degree of narrowing within them.  The two most common areas affected by FMD are the renal arteries (arteries carrying blood to the kidneys) and the carotid arteries (arteries carrying blood to the brain).  Common manifestations related to the artery involved are shown below.   

FMD of Renal Arteries (Kidney):

- High blood pressure [>140/90 mmHg] - Abnormal kidney function as detected on blood tests - Flank pain from dissection or infarction of the kidney - Kidney failure (rare) - Shrinkage (atrophy) of the kidney

FMD of Carotid Arteries:

- Bruit (noise) heard in neck with stethoscope - Swooshing sound in ear - Ringing of the ears - Vertigo (room spinning) - Dizzyness - Headache - Transient ischemic attack - Stroke - Neck pain - Horner's syndrome - Dissection

  People with carotid FMD have a higher risk for intracranial aneurysms (abnormal dilations of the arteries in the brain).  An intracranial hemorrhage (bleeding in the brain) may occur if an aneurysm ruptures.  FMD involving the mesenteric arteries (arteries that supply the intestines, liver and spleen with blood) can result in abdominal pain after eating and unintended weight loss.  FMD in the arms and legs can cause limb discomfort with walking or arm use (intermittent claudication), cold limbs, weakness, numbness or pain. 

 Who has FMD?

  Anyone can have FMD.  However, it is much more common in women.  Most women are typically diagnosed between the ages of 25-50. Some types of FMD are more common in children or teenagers (See Pediatric FMD).  And there are an increasing number of individuals who are being diagnosed later in life (after age 60).    

 How common is FMD? 

  It is difficult to determine how common FMD is in the general population.  This is due to several reasons.  Individuals with mild disease are often asymptomatic and so the disease often goes undetected.   Most studies examining the prevalence of FMD have looked at specific patient populations in whom individuals may have already suffered from serious consequences of the disease.  Since the disease is often not diagnosed, it is likely that FMD is more common than previously thought.  

 How can FMD be diagnosed?

  There are a number of methods that can be used to detect FMD.   These include computed tomographic angiography (CTA) and magnetic resonance angiography (MRA), ultrasound, and catheter based angiogram.  The experience and expertise available at your medical institution will play an important role in what diagnostic options are available to you. 

 In the most common form of FMD (medial fibroplasia), a characteristic “string of beads” appearance is seen in the affected artery.  This appearance is due to changes in the cellular tissue of the artery wall that causes the arteries to alternatively become narrow and dilated.  A less common, but more aggressive form of FMD may cause an area of severe concentric narrowing of the blood vessel (intimal fibroplasia) or long smooth narrowing.

 What kind of treatment is there for FMD?

 There is no cure for FMD.  However, in some cases an attempt should be made to improve the flow of blood through the vessel.  The kind of treatment used for FMD depends largely upon which arteries are affected and the presence and severity of the signs or symptoms.   The experience and expertise available at your medical institution will also play an important role in what treatment options are available to you.   If your health care professionals feel that treatment is warranted, most often percutaneous transluminal angioplasty (PTA) is preferred.  PTA is often performed at the same time as an arteriogram.  Arteriography is a procedure that is performed by a vascular specialist (interventional radiologist, neuroradiologist, vascular surgeon, vascular medicine specialist or cardiologist) with appropriate training. It involves inserting a small tube into or near the affected artery and injecting contrast material, a dye that can be detected by an X-ray machine.  An x-ray of the affected area is then taken and examined.  If an angioplasty is performed, a catheter is extended into the affected artery and a small balloon is inflated that opens the vessel in the area of narrowing.   A metal stent is typically not required to keep the vessel open and under most circumstances should only be used if angioplasty alone was not successful or to treat a dissection (tear) of the artery.   

  The individual is usually awake during the procedure although medications may be given to make the patient more comfortable.  This outpatient procedure usually lasts from one to two hours with a recovery period of up to six hours. It is rarely necessary to have traditional surgery performed unless an aneurysm is present.  Most individuals should take an antiplatelet agent daily (i.e., aspirin).  All patients who use tobacco should be encouraged to quit. The appropriate treatment will vary with each individual and severity of disease.  It should be discussed in depth with a specialist who is knowledgeable about FMD.  

 If I have FMD should I restrict my exercise routine?

 In general there is no contraindication to exercise. But you must check with your physician to help you design an exercise program that is right for you. 

 Is Chiropractic Care Helpful or Harmful?

 Patients with FMD should not undergo high velocity manipulative therapy on the neck or back. Chiropractic manipulation has been associated with carotid and vertebral dissection and since FMD patients are prone to this, they should not undergo this type of therapy. Soft tissue massage is fine for most patients.  

Updated September 2008, by Jeffrey Olin, MD., Mount Sinai, New York and Pamela Mace, RN.  

 FMDSA Frequently Asked Questions were authored by Susan M. Begelman, M.D., Staff Physician, The Cleveland Clinic Foundation.  Updated August 2, 2004.

 

BIBLIOGRAPHY

Begelman, SM and Olin, JW.  Fibromuscular Dysplasia,  Current Opinion in Rheumatology.  (2000) 12:41-47.

Fenves, AZ and Ram, CV.  Fibromuscular Dysplasia of the Renal Arteries, Current Hypertension Reports.  (1999) 1:546-549. 

Lusher, TF, Keller HM, Imhof, HG, Griminger, P, Kuhlmann, U, Largiader, F, Schneider, E, Schneider, J, Vetter, W.  Fibromuscular Hyperplasia: Extension of the disease and therapeutic outcome.  Results of the University Hospital Zurich Cooperative Study on Fibromuscular Hyperplasia.   Nephron.  (1986).  44(Suppl 1): 109-114. 

Lusher, TF, Lie, JT, Stanson, AW. Houser, OW, Hollier, LH, and Sheps, SG.    Arterial Fibromuscular Dysplasia, Mayo Clinic Proceedings.  (1987) 62: 931-952.