Abstract
Fibromuscular Dysplasia (FMD) is “an idiopathic, segmental, non-atherosclerotic and non-inflammatory disease of the musculature of arterial walls, leading to stenosis of small and medium-sized arteries” (Persu, et al; 2014). FMD can lead to hypertension, arterial dissections, subarachnoid haemorrhage, stroke or mesenteric ischemia. The pathophysiology of the disease remains elusive. While familial cases are rare (<5%) in contemporary FMD registries, there is evidence in favour of the existence of multiple genetic factors involved in this vascular disease. Recent collaborative efforts allowed the identification of a first genetic locus associated with FMD. This intronic variant located in the phosphatase and actin regulator 1 gene (PHACTR1) may influence the transcription activity of the endothelin-1 gene (EDN1) located nearby on chromosome 6. Interestingly, the PHACTR1 locus has also been involved in vascular hypertrophy in normal subjects, carotid dissection, migraine and coronary artery disease. National and international registries of FMD patients, with deep and harmonised phenotypic and genetic characterisation, are expected to be instrumental to improve our understanding of the genetic basis and pathophysiology of this intriguing vascular disease.
Highlights
Lesions of two vascular beds or more and 15% of three vascular beds or more
Based on angiographic patterns two subtypes have been defined for renal Fibromuscular Dysplasia (FMD) [1,5,10], and subsequently for cervico-cephalic FMD [1,11], i.e., (i) multifocal FMD: “string-of-beads” appearance, alternation of stenosis and aneurysmal dilations (>80% of cases), corresponding to the medial form according to the former histological classification [12]; and (ii) focal FMD: isolated stenosis, whatever its length, in young patients with few or no cardiovascular risk factors, in the absence of atherosclerotic or inflammatory lesions
We report a case of 3 siblings affected by hypertension and renal artery FMD followed at the Grand Hôpital de Charleroi, Gilly, Belgium (Figure 1), as an illustration
Summary
In view of the predominance of women among FMD patients, a role for female hormones has been assumed. It has been hypothesized that the estrogen-induced production of extracellular matrix proteins from vascular fibroblasts and vascular smooth muscle cells [13], may be responsible for some typical histopathological alterations of FMD [12,14]. Up to now, we lack consistent and powerful data to assess for associations between FMD and e.g., the number of pregnancies, age at menarche, history of hysterectomy, gynaecological problems, spontaneous abortion and/or oral contraceptive therapy [12,15]. All available studies are retrospective, small and underpowered. Large prospective registries are needed to test the female hormonal environment hypothesis
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