Fibromuscular dysplasia ( FMD ) is a non-atherosclerotic, non-inflammatory disease of the blood vessels that causes abnormal growth within the artery walls. FMD has been found in almost every arterial bed in the body although the most commonly affected arteries are renal and carotid arteries.
There are different types of FMD, with the most common multi-focal fibroplasia. Furthermore, less commonly, forms of the disease include focal (formerly known as intima) and adventitial fibroplasia. PMK mainly affects middle-aged women, but has been found in men and people of all ages. The pediatric FMD case is very different from the adult population, and is less studied. The prevalence of FMD is unknown and, although the disease was initially considered rare, recent research suggests that it may be under-diagnosed.
Video Fibromuscular dysplasia
Signs and symptoms
The symptoms expressed by FMD patients are highly dependent on vascular beds affected by the disease. Patients can also be completely asymptomatic and have an accidentally discovered FMD (for example, when imaging is done for other reasons). In a study of the United States Registry for Fibromuscular Dysplasia, the median age on the first symptom was about 47 years.
Kidney artery
The main symptoms associated with renal FMD are secondary hypertension and bruits that can be heard with a stethoscope on the abdomen or pelvis. Complications such as aneurysms, dissection, or occlusion of other renal arteries have been linked to renal artery FMD.
Cerebrovascular region
The carotid and vertebral arteries are most commonly affected. The central and distal regions of the internal carotid artery are often involved. Patients with FMD in the carotid artery usually present around the age of 50 years. Symptoms of craniocervical involvement include headaches (mostly migraines), pulsatile tinnitus, dizziness, and neck pain, although patients are often asymptomatic. On physical examination, one can detect secondary neurological symptoms from a stroke or transient ischemic attack (TIA), a bruit above the affected artery, and a decrease in distal pulsation. Cerebrovascular FMD complications include TIA, ischemic stroke, Horner syndrome, or subarachnoid hemorrhage.
Other sites
Patients with PMD or gut, may experience abdominal pain after eating or weight loss. FMD in the extremities may cause claudication or may be detected by the bruit. If the lower extremity artery is affected, the patient may come with cold feet or proof of distal embolism. The presence of FMD in the subclavian artery can lead to arm weakness, brackets, claudication, and subclavial olfactory syndrome.
Children
Children with FMD often report a variety of non-specific symptoms or present with hypertension during routine physical examination. Symptoms are generally related to the affected arteries. Symptoms may include headache, insomnia, fatigue and chest or abdominal pain. FMD affects the head neck artery is generally recognized as a cause of childhood stroke.
Detection may come from bruits that are present on the affected vascular bed during the physical assessment. However, the absence of bruit does not rule out significant vascular disease.
In children, renovascular disease accounts for about 10% of all causes of secondary hypertension. Kidney failure is a common presentation in infants and children but rarely occurs in adults, although occasionally problems arise in adults with focusing disease. "Presentations in infants and children younger than 4 years are likely to resemble vacancies."
Maps Fibromuscular dysplasia
Cause
While the cause of FMD remains unclear, current theories suggest that there may be a genetic predisposition as case reports have identified disease groups and prevalence among twins. In fact, according to the Cleveland Clinic, about 10% of the cases appear to be inherited and often coexist with other genetic disorders affecting blood vessels. Approximately 10% of patients with FMD have affected family members. A study conducted from a patient registry at the Michigan Cardiovascular Outcomes Research and Reporting Program (MCORRP) at the University of Michigan Health System reported a high prevalence of family history of stroke (53.5%), aneurysm (23.5%), and sudden death ( 19.8%). Although FMD is a family history of non-atherosclerotic hypertensive and hyperlipidemic diseases is also common among those diagnosed with FMD. It is believed that the cause of FMD is not a single identifier such as genetics but has many underlying factors. Theories of hormonal influences, mechanical stresses from trauma and stress to artery walls, as well as the effects of loss of oxygen supply to blood vessel walls caused by fibrous lesions. It has been suggested that environmental factors, such as smoking and estrogen, can play a role other than genetic factors.
Pathophysiology
FMD can be found in almost every artery in the human body, but most often affects the carotid, vertebral, kidney and even arteries that supply the intestines, arms, and legs. Patients may present with FMD in some blood vessels. FMD has been pathologically categorized into three types of classification: Multi-focal, focal, and adventitial; refers to a particular layer of artery walls affected.
Focal
In pediatrics, the most common form of FMD is focal fibroplasia. Focal fibroplasia is described as a long, narrow, irregular or delicate focal stenosis and may occur in any arterial bed. While it is the most common type among children, it accounts for only about 10% of all FMD cases. It most often presents with ischemic symptoms, and is often mistaken for Takayasu arteritis. (formerly known as intimal)
Multi-focal
The second type, multi-focal fibroplasia, involves thickening of the media and the formation of collagen. It is usually reported to have the appearance of a 'string of beads' in an angiography review. "Bead components are often larger than normal arterial lumen, and in a subset of patients with FMD, present aneurysms that may require treatment." The multi-focal subtypes of FMD account for almost 80% to 90% of all FMD cases. (formerly known as medial)
Adventitial
The third classification is adventitial fibroplasia, in which collagen replaces fibrous adventitia and extends beyond the arteries. This form is considered rare but the appearance of angiography may look similar to the focal subtype of FMD, making the difference difficult.
Diagnosis
It is a lack of specific symptoms and its potential to appear anywhere that makes FMD a challenge to be detected early on. The most accurate diagnosis comes from combining clinical presentation and angiographic imagery. According to the Michigan Outcomes Research and Reporting Program (MCORRP, 2013) the length of time from the patient's first sign or symptom for a diagnosis is usually 5 years.
FMD is currently diagnosed through the use of invasive and noninvasive tests. Non-invasive tests include duplex ultrasonography, magnetic resonance angiography (MRA), and computed tomographic angiography (CTA). Invasive testing through angiography is the gold standard. However, because the risk of these higher complications is usually not done early on. Sometimes, FMD is diagnosed asymptomatic after unrelated x-rays present the classic 'string of beads' appearance of the arteries, or when a practitioner investigates an unexpected bruit found during the exam. When FMD diagnosis is considered for the patient's overall medical history, family history and vascular examination should be completed.
The exact diagnosis of FMD can only be made with imaging studies. Catheter-based angiography (by contrast) has been shown to be the most accurate imaging technique: this test involves a catheter inserted into a large artery and progressing to reach the blood vessels. The catheter allows practitioners to see and measure arterial pressure that aids in the categorization and severity of the diseased artery of FMD. According to Olin, "catheter-based angiography is the only imaging modality that can accurately identify FMD changes, aneurysm formation, and dissection in branch vessels." Practitioners believe that it is important to use IVUS imaging because stenosis can sometimes only be detected through pressure gradient or IVUS imaging methods. In addition, computed tomography angiography and magnetic resonance angiography are usually used to evaluate arteries in the brain. Doppler ultrasound can be used both in the diagnosis and follow-up of FMD.
Children
The distinguishing presentation is suggestive of FMD being a unique syndrome with respect to pediatric populations. Experienced FMD doctors do not rely on the angiography of "bead strands" for diagnosis. In fact, it is recommended that FMD may be under and diagnosed excessively in children with stroke.
Treatment
There is no known cure for FMD. However, the treatment focuses on relieving the symptoms associated with it. Medical management is the most common form of treatment. The best approach to medical management of these patients is continually reevaluated as more information is learned about the disease.
Kidney care
Blood pressure control is a major concern when treating patients with renal FMD. In cases of renal stenosis and indications for intervention, percutaneous balloon angioplasty may be recommended. Many studies have assessed percutaneous rates of percutaneous transluminal angioplasty (PTA) in these cases, and have found symptomatic relief of hypertension. Duplex ultrasonography should be performed immediately after this procedure to ensure adequate kidney velocity.
Stents have a level of restenosis of 10-20%, and can make revascularization operations more difficult. Surgical revascularization may be required if the aneurysm develops within the affected artery or if the PTA does not resolve the problem.
Reconstruction of ex vivo renal arteries is sometimes used for complex diseases in which the branches of the renal arteries are affected.
Cerebrovascular treatment
Patients with carotid or vertebral FMD should be medically administered to reduce the risk of stroke. 81 mg aspirin is usually prescribed for patients with carotid FMD. Antiplatelet and anticoagulants can be used to reduce the risk of blood clot formation. If a TIA or stroke should occur, percutaneous angioplasty and antiplatelet therapy may be necessary.
Treatment for FMD in other regions
Little information is known about the best treatment for FMD outside the kidney and extracranial areas. If claudication or extremity ischemia is a result of FMD in the extremities, angioplasty may be implemented.
Children
Pediatric FMD treatment and medical interventions are available. Treatment is determined by factors such as age and location of the disease but routinely involves controlling hypertension, reshaping vascular flow, preventing clots, and improving lifestyles such as diet, exercise and smoking cessation.
Medical therapy for a child population may involve the use of angiotensin inhibitor blocker inhibitors and/or angiotensin II receptor blockers, multiple anti-hypertensive drugs, diuretics, calcium channel blockers, and beta-blockers. Prevention of affected arterial thrombosis can be done through the administration of antiplatelet drugs such as aspirin.
Percutaneous transluminal kidney audioplasty (PTRA) remains the gold standard for renal artery FMD. This treatment is useful when hypertension is difficult to control; patients are intolerant of anti-hypertensive drugs, do not complain about treatment regimens and patients lose kidney volume due to ischemia. PTRA can also help prevent lifelong reliance on drugs for young patients. According to Meyers, "the results of PTRA are effective in controlled or controlled blood pressure, which is often characterized by a reduction in plasma renin activity and angiotensin II levels, and when compared with surgery, percutaneous percutaneous angioplasty is cheaper, can be performed on an outpatient basis, lower morbidity, and the use of stenting is not necessary. "However, there are parts of the pediatric population that are resistant to PTRA. Side effects may include, "recurrent stenosis, arterial occlusion with renal loss, and arterial rupture with extravasation and the formation of a pseudo aneurysm and may require surgical intervention.
Prognosis
Prognosis and research results are still lacking. In some cases if not properly managed an associated FMD aneurysm may occur causing bleeding to the brain, resulting in a stroke, permanent nerve damage, or death. Shedding light in the importance of detection and seeking proper care in reference to results. What we know is that patients with multi-focal fibroplasia generally have a favorable prognosis. However, those present with FMD in some vascular beds, or focal diseases involving multiple branches of the renal artery may develop renal artery dissection or progressive renal impairment. Therefore, it has a more difficult and complex prognostic course. There is currently no specific study or report on long-term prognosis and FMD outcomes in children.
Related diseases
The vascular subtype of Ehlers-Danlos Syndrome (type IV) has been associated with a multi-focus FMD. This syndrome should be suspected in patients with multiple aneurysms and/or tears (dissection) in the arteries in addition to typical angiographic findings of FMD. There are separate reports of FMD associated with other disorders, including Alport syndrome, pheochromocytoma, Marfan syndrome, Moyamoya disease, and Takayasu arteritis.
References
Quote
- 1Baert AL, Wilms G, Amery A, Vermylen J, Suy R. percutaneous transluminal kidney angioplasty: preliminary results and long-term follow-up in 202 patients. Cardiovasc Int Radiol. 1990; 13; 22-28
- Tegtmeyer CJ, Selby JB, Hartweel GD, Ayers C, Tegtmeyer V. Results and angioplasty complications in Fibromuscular disease. Circulation. 1991; 83 (suppl); I-155-I-161.
- Mettiger KL, Ericson K. Fibromuscular dysplasia and brain - observations on angiography, clinical and genetic characteristics. Blow. 1982; 13; 46-52.
- Schievink WI. Spontaneous dissection of the carotid and vertebral arteries. N Engl J Med. 2001; 344; 898-906.
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