Fibromuscular dysplasia overview
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Management of Patients With Fibromuscular Dysplasia of the Extracranial Carotid Arteries |
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Mohsen Basiri M.D.
Overview
The definition of Fibromuscular Dysplasia(FMD) on the Medical Subject Headings is "an idiopathic, segmental, nonatheromatous disease of the musculature of arterial walls, leading to stenosis of small and medium-sized arteries. There is a true proliferation of smooth muscle cells and fibrous tissue formation. however, this systemic arteriopathy is a noninflammatory process and is therefore not associated with inflammatory biomarkers.
According to the definition, FMD is a condition which can involve every vascular bed in the body, therefore it can cause very heterogeneous and extensive spectrum of clinical manifestations from asymptomatic involvement to devastating consequences and morbidity and mortality.
Unlike routine conception that FMD is a rare disease of middle-aged female, current data from the French and US registries showed that the awareness about FMD must be raised, and every health provider at any level should be familiar with suggestive symptoms and signs of FMD which is more frequent and more often systematic than previously thought.
Historical Perspective
Fibromuscular dysplasia was first discovered by Leadbetter and Burkland, in 1938 following evaluation of severe hypertension in a 5-year-old boy. The first histopathological description of fibromuscular dysplasia and pathologic classification for this condition was proposed in 1958 and 1971 by McCormack and coworkers, chronologically.
Fibromuscular dysplasia with involvement of extrarenal arteries has been considering in recent years. However numerous aspects of molecular biology and genetic etiology of this condition remain unanswered, and there are various top research priorities in the field of FMD to improve our understanding of this condition.
Classification
- The classification system for fibromuscular dysplasia (FMD) was first according to the arterial layer involved. (tunica intima, tunica media , or adventitia) . However, with use of transluminal percutaneous angioplasty (TPA) for treatment of FMD lesions and its preference rather than surgery, the obtaining of pathological specimens are restricted. Thus, today, FMD is a disease diagnosed radiographically and histopathological classification has been replaced by the arteriographic findings.
Pathophysiology
- In Fibromuscular dysplasia, the proliferation of vascular smooth muscle of one or more small or medium-sized arteriesundergo dysplasia and cause stenosis. this abnormal cellular development is characterized by fibrous thickening of the intima, media, or adventitia of the involved arteries; which ultimately lead to arterial narrowing.
Causes
The cause of fibromuscular dysplasia has not been identified. To review risk factors for the development of FMD, click here.
Differentiating Xyz from Other Diseases
- Fibromuscular dysplasia must be differentiated from other diseases that present clinical features of multisystem involvement, hypertension, aneurysm, and dissection, such as atherosclerotic vascular disease, vasculitis, and Ehlers-Danlos Type IV.
- There is a significant delay in diagnosis from the first onset of clinical symptoms/signs of 4.4 years in men and 4.1 years in women. There are several possible reasons for such a delay, including the possibility that FMD is not considered in the differential diagnosis of a patient’s symptoms because of under-recognition of this disorder, the mistaken belief that FMD is predominately a rare disease of young patients, and the fact that many of the signs and symptoms of FMD are nonspecific, such as dizziness, tinnitus, and headaches.
Epidemiology and Demographics
Risk Factors
There are no established risk factors for fibromuscular dysplasia; neverteless there are evidences that cigarette smoking, hypertension and other classic risk factors for atherosclerosis may be risk factors in the development of FMD .
However FMD has a greater prevalence among women but no definite association has been
found between this condition and use of oral contraceptives or disturbances of endogenous sex hormones. Since the disease is more common among the first-degree relatives of patients with FMD, Genetic factors may play a role in the development of FMD.
Screening
Natural History, Complications, and Prognosis
Diagnosis
Diagnostic Study of Choice
Catheter-based angiography is the gold standard test for the diagnosis of renovascular fibromuscular dysplasia. Imaging modilities are the methods for diagnosing FMD. Duplex ultrasonography, accompanied by computed tomographic angiography(CTA), and magnetic resonance angiography (MRA), are imaging techniques for detecting FMD lesions but the gold standard remains catheter-based angiography.