What is fibromuscular dysplasia (FMD)?
Fibromuscular dysplasia (FMD) is a condition that affects the arteries that take blood from the heart to the rest of the body. It can cause damage to the tissue of the kidneys and affect their ability to work properly.
FMD does not always cause any symptoms, so it is hard to tell how many people are affected. It could be as many as 1 in 250 people, although the majority will not need any treatment. Around 8 in 10 people with FMD are women, usually aged 25 to 50.
What are the signs and symptoms of FMD?
Many people with FMD do not have any symptoms. For those who do, symptoms are usually linked to high blood pressure and include:
- blurred vision
- chest pain
Other symptoms may include:
- abdominal pain after eating
- ringing in the ears (tinnitus)
- weakness or numbness in the face
- cold hands and/or feet.
FMD rarely causes kidney failure.
What causes FMD?
The exact cause of FMD is not yet known. Hormones and environmental factors are likely to be involved as the condition is much more common in middle-aged women than any other group. However, it can occur in men and women of all ages.
There may also be a genetic link as there have been cases of multiple family members being affected. However, research into this aspect is still ongoing.
FMD causes patches of abnormal cell growth in the arteries that supply various organs in the body, including the heart, brain and kidneys. These can cause the arteries to narrow and/or bulge, which can lead to tears and leakages, affecting the blood flow.
The kidneys are the most common organ to be affected by FMD. A reduction in the blood supply to the kidneys leads to an increase in blood pressure, which can affect how well the kidney is able to work.
FMD is more common in people who smoke, although the reason for this is not yet known.
How is FMD diagnosed?
As FMD often does not cause any symptoms, it may only be picked up when having a test for another condition. It is found in around 1 in 25 people who put themselves forward to be living kidney donors.
FMD is diagnosed by a scan of the blood vessels. There are several different ways in which this can be done:
- Duplex ultrasound – a device called a transducer is pressed against the skin and sends sound waves into the body. This creates a colour map of the arteries to show their size and shape and the direction of blood flow.
- CT angiogram – a harmless dye is injected into the body which shows the arteries up on a scan.
- Catheter angiography – a thin tube (catheter) is inserted in an artery and dye and X-rays are used to look at its size and shape.
FMD usually shows up as a ‘string of beads’ on imaging tests of the arteries.
Does FMD affect other parts of the body?
FMD can affect other parts of the body, depending on which arteries are involved.
If it affects the arteries in the neck, the blood supply to the brain may be reduced. This can cause problems ranging from face and neck pain to vision problems and an increased risk of stroke.
If FMD affects the arteries that supply blood to the limbs, intestine, liver or spleen, it can cause pain and a change in normal function.
Does FMD run in families?
Around 1 in 10 people with FMD also have a family member with the condition which suggests a genetic basis, however this has not yet been fully identified.
How is FMD treated?
There is currently no direct cure for FMD, so treatment focuses on reducing blood pressure with medications known as angiotensin converting enzyme (ACE) inhibitors or angiotensin receptor blockers (ARBs).
Aspirin may be prescribed to thin the blood to help reduce the risk of stroke.
To improve the flow of blood through a narrowed artery, a procedure called an angioplasty might be performed. This takes place under a local anaesthetic and involves a thin tube being inserted into the affected artery and a small balloon being inflated within the artery itself. Sometimes a metal stent will be inserted to keep the artery open and improve blood flow. Occasionally it is not possible to complete this procedure under a local anaesthetic and an operation will be needed.
FMD is more common and more serious in people who smoke so help to stop smoking will be offered if it is needed.
Where can I get more information or support about FMD?
For more information on FMD, including its diagnosis, symptoms and treatment, visit the Fibromuscular Dysplasia Society of UK & Ireland’s Facebook group.
Publication date: 11/2023
Review date: 11/2026
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