PREVALENCE AND CHARACTERISTICS OF FAMILIAL FIBROMUSCULAR DYSPLASIA IN THE EUROPEAN/INTERNATIONAL FMD REGISTRY (FEIRI)

Objective: Reported prevalence of familial fibromuscular dysplasia (FMD) varies between 3 and 11%, depending on center and screening policies. However, the characteristics of affected relatives are usually poorly described. The objective of this study was to look for the prevalence and characteristics of familial FMD in the FEIRI registry. Design and method: The FEIRI database (n= 2500) was screened for familial cases, defined as presence of FMD-lesions or aneurysm/ dissection in at least one relative. Centres reporting familial cases were contacted to complete a standardized CRF about affected relatives. Whenever possible, images of lesions were obtained. The prevalence of familial cases and characteristics of index patients (group 1) and affected relatives with typical FMD (group 2) or aneurysms/dissections without stenotic FMD-lesions (group 3) were analyzed. Results: 46 familial clusters were identified in 5 centres (prevalence 2-14%). The characteristics of index patients (n=46) were in line with those reported in international registries (mean age 51 ± 13 years, 78% women, 96% multifocal), but with a higher prevalence of aneurysms (52%) and dissections (41%). Affected relatives with (group 2, n=32) or without (group 3, n=26) typical stenotic FMD lesions differed substantially from index patients. Age at FMD diagnosis was similar in group 2 (51 ± 14y), but higher in group 3 (60 ± 15y) (p<0.05). The proportion of men increased across groups 1-3 (22%, 28% and 38%, respectively). The prevalence of multifocal FMD was similar in group 2 vs. group 1 (97%), while patients in group 3 had mostly aneurysms (85%) but less dissections (23%). Symptomatic cases (mostly hypertension or stroke) accounted for 91% in group 1, 63% in group 2 and 42% in group 3. Conclusions: FMD patients found to have affected relatives, accounted for 6% of cases in a limited number of expert centres. Their main characteristics were similar to those of FMD patients overall, with the exception of a higher proportion of aneurysms and dissections. Affected relatives without stenotic FMD lesions had mostly aneurysms, were older and included a higher proportion of men compared to both index patients and relatives with typical FMD.