Fibromuscular Dysplasia

Fibromuscular dysplasia, first observed by Leadbetter and Burkland, is a rare vascular condition that mostly affects the arteries supplying blood to the kidneys (renal arteries) and brain (carotid and vertebral arteries).

Location of FMD in other parts of the body are the mesenteric arteries, coronary arteries, arteries to the arms (brachial arteries) and those to the legs (iliac arteries), subclavian and axillary arteries, femoral arteries or hepatic arteries and temporal arteries.

FMD Types: Pathologic Classification

On the basis of an arterial wall involvement, FMD can be classified into three types such as:

Medial dysplasia
- Medial fibroplasias (75–80%)
- Perimedial fibroplasias (10–15%)
- Medial hyperplasia (1–2%)

Intimal fibroplasias (<10%)
Adventitial fibroplasia (<1%)

Causes

Fibromuscular dysplasia occurs when the fibrous tissue and muscle layers in the middle of the medium and large arterial walls of the body have abnormal cellular development. This leads to the subsequent narrowing (stenosis) and enlargement (an aneurysm) and even tears (dissections) of the arteries.

Risk Factors

Though it can affect both adults and children, studies have suggested some possible risk factors:

Gender: About 90% of those affected are women

Age: Premenopausal women are at a greater risk than men, suggesting possible hormonal influences

Genetic pattern: According to certain studies, about 10% of people diagnosed with FMD have a relative suffering from this condition.

Birth defect: abnormal position of the arteries at birth may also lead to the condition.

Smoking: The disease seems to aggravate in persons who smoke.

Signs and Symptoms

The symptoms, mainly depending on the affected artery may not be detectable in some people having the disease.

Symptom of FMD of renal artery (kidney)

A discomfort felt in the upper abdomen or back and sides.

FMD of the carotid arteries (brain)

Headache
Dizziness
Swooning ringing in ears called pulsatile tinnitus
Room spinning sensation or vertigo
Neck pain implying carotidynia
Hazy vision including drooping eyelids
Numbness felt in the face

FMD of the mesenteric arteries

Abdominal pain after eating
Changes in the color or appearance of skin
Hands and legs feeling numb, cold and weak
Sudden weight loss

FMD of the extremities or the brachial arteries and iliac arteries

Discomfort in the limbs while doing exercise or moving

FMD of coronary artery (heart)

Chest pain

FMD may also lead to the development of tears in the walls of the coronary arteries called spontaneous coronary artery dissection or SCAD, which may induce symptoms as

Shortness of breath
Sweating and nausea

Complications

Heart attack
High blood pressure or renovascular hypertension characterized by a potassium deficiency (hypokalemia) and renal murmurs (renal bruit)
Carotid dissection
Aneurysms
Pain or cramps felt in lower legs or intermittent claudication
Ischemic renal atrophy
Stroke
kidney failure (rare)
Organ dysfunction
Rupture of the inner wall of the aorta called aortic dissection

Diagnosis

Along with a discussion of family history, a routine examination of abdomen or neck is done to detect a swooshing noise called a bruit that signifies an abnormal blood flow. Once FMD is diagnosed in a particular body area, the other blood vessels are also checked to determine further blockage of arteries.

The radiology studies are:

An X- ray or scan may be done to look for the beaded appearance of the arteries usually referred to as a “string of beads.”

Catheter-based angiography is an accurate imaging test that can be done by inserting a catheter or a long, slender tube into a large artery and slowly extending it to the concerned blood vessel. An accurate radiographic image of the arteries is then obtained.

Computer tomography angiogram (CTA) which makes a combination of X- rays, contrast dyes and computer technology to obtain 3 dimension images of the arteries.

Magnetic resonance angiography (MRA) which employ a combination of radio frequencies and computer to derive detailed pictures of the cluster of cells that narrow the artery.

Duplex ultrasound or Doppler by which images of blood vessels, tissues and organs are obtained through the application of high-frequency sound waves and computer.

If these tests do not give satisfactory results, then therapeutic procedures such as balloon angiography, or an angiogram dye test are done.

Differential diagnosis

Atherosclerotic stenosis
Stenosis linked with type 1 neurofibromatosis
Vascular Ehlers- Danlos syndrome
William’ syndrome
Polyarteritisnodosa
Vasculitis
Neurofibromatosis

Fibromuscular Dysplasia Treatment

FMD is treated on the basis of the patient’s overall health, the area where the artery has been affected, and any existing conditions such as high blood pressure. The treatment procedures are:

Medications

Angiotensin-converting enzyme inhibitors (ACE) and Angiotensin II receptor blockers

If there is high blood pressure in the renal arteries (renovascular hypertension), these medications may be prescribed to prevent the narrowing of blood vessels or renal artery stenosis. ACE inhibitors include medications as enalapril (Vasotec), benazepril (Lotensin) and lisinopril (Zestril). Angiotensin II receptor blockers include medications such as irbesartan (Avapro), candesartan (Atacand) and valsartan (Diovan).

Diuretics

Blood pressure can also be controlled by using diuretics like hydrochlorothiazide (Microzide).

Beta Blockers and Calcium Channel Blockers (CCB)

Metropol (Toprol- XL, Lopressor) and atenolol (Tenormin) are the beta blockers that may slow the heart rate and block adrenaline. CCBs like nifedipine (Procardia, Adalat) can ease the blood vessels.

Surgery

An invasive surgery, mostly aortorenal bypass is undertaken if the arterial narrowing is severe. It mainly depends on the area affected and the extent of damage. It involves removal of the blocked portion of the artery or forming a bypass around the block. Most patients with brain aneurysms may be treated with an open surgery.

Percutaneous Transluminal Angioplasty (PTA)

PTA is done in patients who suffer from uncontrollable blood pressure or are unresponsive to medication. In patients with renal FMD, PTA leads to controlled blood pressure indicated by a decrease in the activity of the hormone, rennin, while it may prevent strokes in patients having carotid FMD.

Angioplasty for patients with renal Fibromuscular Dysplasia is done without placing a metallic stent whereas; it is needed for patients with carotid or vertebral FMD who have got a tear.

FMD Alternative Treatment

Psychological treatment may be given to tackle stress and anxiety.

Patients having FMD can be given gynecological advice regarding the use of oral contraceptives or estrogen therapy that can influence blood flow in arteries.

Follow-up

Even though FMD can be managed successfully, there are chances of its recurrence. Hence, the follow-up of patients generally consists of regular check-up of blood pressure, surveillance imaging every 6 to 12 months along with carotid and renal ultrasound to keep a record of the progress.

Prevention

Though it is difficult to prevent Fibromuscular Dysplasia, yet having a healthy diet consisting of fresh vegetables, fruits, and salad may help.

Prognosis

The prognosis depends on the severity of the symptoms and the complications that develop. However, patients with FMD usually have an average life expectancy. But in rare cases, intense FMD can result in nerve damage, bleeding in the brain and even death.

Prevalence

According to several reports, amidst the few thousand cases of FMD, the prevalence of renal artery FMD is about 65% – 75%, cerebrovascular involvement is about 25% – 30%, visceral involvement is nearly 9% and the prevalence of FMD of the arms and legs is 5%.

ICD-9 and ICD- 10 Codes

The ICD- 9 code used for referring to the ailment is 447.8, while the ICD- 10 code is 177.3.

Reference

Fibromuscular Dysplasia

Fibromuscular Dysplasia

FMD Types: Pathologic Classification