Fibromuscular Dysplasia

What is Fibromuscular Dysplasia?

Renal artery stenosis, which is often the primary reason for high blood pressure caused by another condition (secondary hypertension), is usually due to a disease that hardens the arteries supplying the kidneys, known as atherosclerotic renovascular disease. A less common cause, found in 10% to 20% of cases, is a rare and less understood disease called Fibromuscular Dysplasia (FMD). This disease affects mainly younger women and damages the muscular cells in arteries.

FMD typically affects the renal and carotid arteries (the arteries that supply blood to the kidneys and neck), but can affect any artery in the body. It often causes high blood pressure due to damage to the renal artery (known as renovascular hypertension) but can also lead to stroke in young adults. FMD can also affect the arteries of the heart, the main artery of the body (aorta), and the arteries of the lungs (pulmonary artery).

Notably, diagnosing and treating FMD early is crucial, as this has a significant influence on long-term outcomes.

What Causes Fibromuscular Dysplasia?

Fibromuscular dysplasia (FMD) is a condition that’s still not well-understood despite a lot of research. It’s thought to be connected to both environmental and genetic factors. For example, identical twins have been known to both have FMD, which suggests that the condition could be inherited.

A past study that reviewed the health history of 104 patients with FMD in the kidneys found that in 11% of those cases, at least one brother or sister also showed signs of kidney FMD when given a specific type of X-ray test called an angiogram.

Researchers have also noticed a link between certain gene variations in patients and FMD. Smoking has also been considered as a possible cause. The issue appears more frequently in the right kidney than the left, which has led to suggestions that factors related to the kidneys’ movement and position may play a role.

The fact that more women get FMD than men might hint at a connection to estrogen, a hormone primarily produced by women. However, one study reported that the number of pregnancies a woman has had doesn’t affect her risk of developing FMD.

FMD can sometimes be seen along with other conditions, including Marfan syndrome, tuberous sclerosis, Alport syndrome, medullary sponge kidney, pheochromocytoma (a rare tumour of the adrenal glands), collagen 3 glomerulopathy, cystic medial necrosis (a weakening of the aorta’s walls), coarctation of the aorta (a narrow aorta), a deficiency in a protein called alpha-1 antitrypsin, Ehlers-Danlos syndrome, neurofibromatosis type 1, and Williams syndrome.

To sum up, while we have gathered some clues, the reason why FMD develops still remains a mystery.

Risk Factors and Frequency for Fibromuscular Dysplasia

Fibromuscular dysplasia (FMD) is a condition that was first identified in the renal arteries in 1938 and later in the craniocervical arteries in 1946. The exact number of people affected by FMD is unknown. However, it is estimated that 0.4% of the population has renal FMD, and only 0.1% of people have craniocervical FMD. Previous studies have suggested that the prevalence of renal FMD could be higher, with data ranging from 1.1% to 6.6%. A specific study showed that nearly 5.8% of older patients with high blood pressure and renal complications were found to have FMD. These studies suggest FMD is often not diagnosed because many cases don’t show symptoms.

FMD is more common in women under 50, with a ratio of women to men affected beingAbout 15% of patients also have bilateral involvement, which means both sides of the body are affected.

• FMD is a condition that affects the renal and craniocervical arteries.
• 0.4% of people have renal FMD, and 0.1% have craniocervical FMD.
• Some studies suggest the prevalence of renal FMD could be anywhere from 1.1% to 6.6%.
• About 5.8% of older adults with high blood pressure and kidney complications have FMD.
• FMD is more common in women under 50.
• The ratio of women to men affected is 3:1 or as high as 9:1 according to some records.
• The average age of a patient with FMD is 48 years old.
• No particular race or ethnicity is more susceptible, but it’s seen more in Caucasians than in Blacks.
• About 15% of patients with FMD have it on both sides of the body.

Signs and Symptoms of Fibromuscular Dysplasia

Fibromuscular dysplasia (FMD) is a condition that affects the blood vessels in various parts of the body. The symptoms of FMD depend on which blood vessels are affected. If someone in your family has had a stroke or high blood pressure at a young age, you may be at a higher risk for this condition.

Renal FMD, affecting the kidneys, can lead to high blood pressure that is difficult to manage. It can also cause:

• Kidney artery tear
• Flank pain
• Blood in urine
• Kidney damage due to lack of blood supply
• Low potassium levels due to overproduction of a hormone called aldosterone
• A sound (bruit) heard over the abdomen when examined with a stethoscope

Diagnosis of renal FMD may lead to checking for similar issues in the neck and head arteries to prevent severe complications. Craniocervical FMD, affecting the head and neck, can be symptomless or may cause:

• Headache
• Tinnitus – a sensation of hearing a sound when no external sound is present
• Dizziness
• Neck artery tear
• Neck pain
• Stroke
• Horner syndrome – a condition affecting the face and eyes
• Subarachnoid hemorrhage – bleeding within the layers of the brain
• A sound (bruit) heard over the carotid artery in the neck

Mesenteric FMD, affecting the intestines, can cause:

• Weight loss
• Tiredness
• Abdominal pain after eating
• A sound (bruit) heard over the upper abdomen

Subclavian FMD, affecting the blood vessels of the upper arm, can lead to:

• Weakness in the upper arm
• Tingling sensations
• Leg cramps during exercise due to poor blood circulation
• Steal syndrome – a situation where a blood flow pattern in the body changes due to a blockage

Lower limb FMD, affecting the blood vessels in the legs, can cause:

• Leg cramps during exercise
• Cold feeling in the legs
• Decreased blood flow to the feet

Lastly, coronary FMD, affecting the heart’s blood vessels, can cause:

• Chest pain
• Breathing difficulties
• Acute coronary syndrome – a condition where blood supply to the heart is suddenly blocked

Testing for Fibromuscular Dysplasia

If your doctor suspects that you have fibromuscular dysplasia, which is an abnormal growth in the walls of your arteries, there are several techniques they might use to diagnose this condition.

One of these techniques is called Duplex Ultrasonography, which is a type of Doppler ultrasound. This is normally the first screening test for fibromuscular dysplasia. The ultrasound can show signs of turbulence, twists and turns, increased speeds, and resistance in the middle and end of the artery, which suggest fibromuscular dysplasia. However, the effectiveness of the ultrasound can vary depending on the person performing it and can be affected by obesity, movement of the kidney during breathing, and bowel gas.

Your doctor might also use a test called Computed Tomography Angiography (CTA), which is a type of X-ray that can create detailed images of your blood vessels. It is a reliable, non-invasive way to diagnose fibromuscular dysplasia. The CTA can reveal a pattern of artery thickening that looks like a string of beads, which is a typical sign of fibromuscular dysplasia. It can also show kidney aneurysms and infarcts, which are areas of tissue damage caused by lack of blood flow.

Another technique that might be used is Magnetic Resonance Angiography (MRA), which uses magnets and radio waves to produce images of the arteries. This has similar sensitivity and specificity to CTA but doesn’t expose you to any radiation or the risk of kidney injury from contrast dye. However, it can’t be used in patients with advanced kidney failure. Studies have shown that MRA is very accurate compared to conventional angiography.

Lastly, your doctor might use an Arteriography. This is a type of X-ray imaging used to visualize the inside of the blood vessels and organs of the body, with particular interest in the arteries, veins, and heart chambers. This is known as the gold standard to diagnose FMD. It not only provides the best images but also allows the doctor to perform endovascular therapy at the same time, which means fixing the issue from inside the blood vessels. Arteriography can also measure the pressure across narrowed parts of the artery. A pressure difference of more than 10% is considered significant stenosis, or narrowing, of the artery. New diagnostics like intravascular ultrasound can further improve the angiography and help check for restenosis, or re-narrowing of the artery following treatment.

Treatment Options for Fibromuscular Dysplasia

Fibromuscular dysplasia (FMD) is a medical condition that often requires different treatment strategies. These may include controlling risk factors, managing blood pressure, and preventing things called ischemic events that occur when blood flow to a certain part of your body is reduced.

When FMD shows up with a warning sign of a possible stroke, known as a transient ischemic attack (TIA), doctors might try to treat it with clot-dissolving medicine or a procedure called percutaneous thrombectomy. This procedure removes the clot from your blood vessels. FMD should be considered if a young person has a stroke. If FMD is spotted on medical images before the person has any symptoms, then medications that prevent blood clots may be given.

Occasionally, FMD can cause a tear in the walls of the blood vessels, known as artery dissection. This is usually managed with blood-thinning medications for 3-6 months once any bleeding issues have been ruled out.

Controlling high blood pressure is key in the treatment of FMD related to the kidneys. Certain medications like angiotensin-converting enzyme inhibitors or angiotensin receptor blockers are often used because of their ability to affect the renin-angiotensin-aldosterone system, a hormone system that plays a big role in regulating blood pressure and the balance of fluids in your body. Doctors keep an eye on kidney function during treatment as there could be some complications if the person has narrowing in both kidney arteries or only has one kidney. Other drugs to lower blood pressure might be added as required.

Quitting smoking can really help because FMD often gets worse more quickly in smokers compared to non-smokers. Despite some uncertainties, doctors may deem it reasonable to administer anti-platelet therapy, such as aspirin, to all FMD patients who’ve had an ischemic event like a stroke.

Sometimes, less invasive treatments might not be enough to manage FMD. In these cases, procedures to restore blood flow to the affected organ, called revascularization, can be needed. For example, young adults with severe blood pressure that is not improving with medication, or patients with aneurysms or dissections, might undergo revascularization. In FMD that affects the carotid artery in the neck, revascularization might be considered for patients with recurrent cerebral ischemia (lack of blood flow to the brain), pseudoaneurysm, or if they can’t tolerate standard treatments. Unfortunately, it’s not possible to perform a surgical procedure called endarterectomy in FMD because the lesions are extremely fibrotic.

In most cases, an approach called percutaneous transluminal angioplasty (PTA) is the first choice for revascularization. This non-surgical procedure is designed to open up blocked blood vessels. It has a high success rate and can cure high blood pressure in 60% to 80% of patients. Despite the success of the procedure, it’s also associated with some risks, and about 6% of people who undergo this procedure may experience complications like a hematoma (a collection of clotted blood) or a blood clot.

While surgical revascularization is an option, it’s usually only recommended for patients with smaller renal arteries or those who didn’t respond to PTA. Regardless of the type of treatment used, doctors will recommend regular follow-up visits with ultrasound tests to monitor the patient’s condition.

What else can Fibromuscular Dysplasia be?

When trying to diagnose fibromuscular dysplasia (FMD), a condition that affects the medium and large arteries in your body, doctors consider other conditions that could be causing similar symptoms. Some of these might be:

• Atherosclerotic Renal Artery Stenosis: Just like FMD, this affects the arteries, but typically around the heart or kidneys. It usually affects older people, and the narrowing of the arteries is near the beginning of the artery, unlike FMD where the narrowing is in the middle or end of the artery.
• Vasculitis: This is an inflammation of the blood vessels. It differs from FMD because it is marked by a lot of inflammation.

There are also some rare conditions that could be mistaken for FMD, but each comes with its unique traits and genetics. These conditions include Marfan syndrome, tuberous sclerosis, Alport syndrome, alpha-1 antitrypsin deficiency, Ehlers-Danlos syndrome, neurofibromatosis type 1, moyamoya, and Williams syndrome.

Another condition that can look like FMD in x-rays is Segmental arterial mediolysis. However, this is distinguished from FMD through its unique characteristics under a microscope, mainly the breakdown of muscle cells in the outer layer of the artery.

What to expect with Fibromuscular Dysplasia

Fibromuscular dysplasia (FMD), a condition that causes abnormal growth in the walls of the body’s arteries, lacks long-term data about its prognosis, or how the disease might progress and affect a person’s health over time. According to the American Heart Association, it’s uncommon for FMD to worsen over time, but it’s also difficult to accurately monitor any progression of narrowness in the arteries due to the condition.

At this point, experts generally view FMD as a harmless disorder that’s usually discovered by chance during medical exams for other issues. However, when FMD affects the cranial nerves, or the nerves in the brain, it can lead to severe health outcomes, particularly in young people.

Furthermore, FMD can also cause a condition called arterial dissection, which is a medical emergency where the inner layer of an artery tears. This can have potentially disastrous consequences.

Possible Complications When Diagnosed with Fibromuscular Dysplasia

Fibromuscular Dysplasia (FMD) commonly affects the kidneys, heart, and neck arteries. When these arteries are involved, it can lead to several complications.

Here are the potential complications:

• High blood pressure (hypertension)
• Tearing in the arteries (dissection of arteries)
• Bulging, weak areas in the arteries (aneurysm of arteries)
• Stroke, a condition that occurs when the blood supply to the brain is interrupted or reduced

Preventing Fibromuscular Dysplasia

For those with a condition called fibromuscular dysplasia (FMD) who have experienced strokes, it’s crucial to understand the details about the disease. FMD affects the walls of arteries, the vessels that carry blood to vital parts of your body. Understanding more about FMD helps people spot future signs that the disease is getting worse or causing other issues.

It’s also key to learn about other factors that could increase the chance of having a stroke. Things that could help include resisting the urge to smoke, eating healthily, and keeping blood sugar levels in check.

Moreover, those with FMD should be aware of the risk of arterial dissection, a condition where the inner layer of an artery tears, which can cause severe health problems. To lower the risks, people with FMD should be careful to avoid neck injuries and avoid rough or abrupt neck movements.