Fibromuscular dysplasia

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Compiled by Bofinger, posted at FMDFAQS

What is Fibromuscular Dysplasia (FMD)? FMD is a disease of blood vessels that causes narrowings (stenosis) and balloonings (aneurysms). It is different to atherosclerosis, or "hardening of the arteries". There is no inflammation of arteries, which distinguishes it from vasculitis, where inflammation is present. Five pathological subtypes of FMD have been described. By far the commonest is "medial fibroplasia", which usually produces alternate narrowing and ballooning, the classic "string of beads" appearance on angiography.

Which arteries are affected? Involvement of the kidney arteries is most commonly recognised, usually because of the development of high blood pressure. The arteries to the brain and the legs are also commonly affected. Less commonly, involvement of the arteries to the bowel and the heart may be apparent.

Who does FMD affect? FMD affects women three times as often as men. The most common age at diagnosis is between 30 and 50 years, however, any age may be affected.

How common is FMD? Disease of the kidney arteries accounts for between 1-in-50 and 1-in-20 cases of high blood pressure seen at high blood pressure clinics, and for up to 1-in-5 children with high blood pressure. FMD is the most common kidney artery disease causing high blood pressure in patients younger than 40. Estimates of how common FMD is depend upon the way it is looked for. FMD has been found in 1-in-50 to 1-in-8 people with normal blood pressure, and approximately 1-in-10 patients undergoing investigation for underlying causes of high blood pressure. FMD may, therefore, be more prevalent than previously appreciated, and almost certainly remains undiagnosed in less severely affected patients.

How may FMD present? FMD predominantly affects young females and can lead to high blood pressure and stroke. FMD is frequently not detected until damage to organs has occurred, so that shrinkage of the kidney is unfortunately often present at diagnosis. Interference with blood circulation to the brain, legs or bowel may also produce symptoms. With increasing age, atherosclerosis becomes the most common cause of these symptoms.

How is FMD diagnosed? FMD may be suspected in patients, particularly young patients, presenting with any of the problems mentioned above. Blood flowing through narrowed arteries produces turbulence which may be heard with a stethoscope. This is called a bruit. Ultrasound scans can detect turbulence and changes in blood flow in a wide range of arteries. Nuclear (or radioisotope scans) of the kidneys may show reduced or delayed blood flow to one or both kidneys. All of these can indicate that there is a narrowing of an artery, however, only angiography (the injection of dye into the artery) can definitely diagnose FMD. The most common lesion is the multifocal lesion, consisting of alternating narrowings and widenings of the artery producing a "string of beads" appearance. Less commonly, lesions may appear as focal (short, single) or tubular (long narrowings of even diameter).

How is FMD treated? The first step is to determine if FMD is responsible for the presenting problem. For example, a patient may have high blood pressure and FMD, but not high blood pressure caused by FMD. In a patient with high blood pressure, the measurement of renin levels in the veins draining the kidneys is essential in determining the relationship of the FMD to high blood pressure. The results of all tests together with the patient's blood pressure level, any effects of the blood pressure on the heart, and any other medical conditions are all considered. If treatment is indicated, angioplasty,(News) where a balloon is inflated inside the artery to open it up, is the preferred and usual treatment. If, as is rarely the case, the lesionis not suitable for angioplasty, an operation may be possible and recommended.

What causes FMD? At this stage, the cause of FMD is unknown.(Medical journals) The following facts are known and may provide clues to the cause:

Females are most frequently affected The most common age for diagnosis is between 30 and 50 years In the kidney arteries, involvement is most often on the right or bilateral Several arteries may be affected in the one patient More than one member of a family may be affected. FibroMuscular Dysplasia. Message Board