Characteristics of Children and Adolescents With Fibromuscular Dysplasia: A Systematic Review and Meta-Analysis

Objective: Based on data from large international FMD registries, the clinical presentation of FMD in adult patients is now well established. By contrast, characteristics of FMD in children and adolescents remain poorly described, and evidence is limited to case reports and small series. We present here the first systematic review and meta-analysis of pediatric FMD, synthesizing available evidence and comparing findings with those obtained in adults. Design and method: Seven databases were systematically searched for clinical studies published since 2000 reporting the characteristics of FMD in children and adolescents. Studies in which focal stenosis was attributed to known pediatric syndromes were excluded. Data were pooled using random-effects models. Subsequently, the characteristics of pediatric FMD patients were compared with those of adult patients with FMD included in the US and FEIRI registries. The meta-analysis was registered in PROSPERO (CRD420251236573), and reporting followed the MOOSE guideline. Results: Nine retrospective studies totalizing 218 children or adolescents with FMD were identified. All had renal FMD and 93.7% were revascularized. The mean age at FMD diagnosis was 11.7 years. Fifty-two % were females (adults in large registries: US Registry 94.7%; FEIRI 81.5%). Most patients (66.6%) had focal FMD (US Registry 24.0%; FEIRI 28%). Despite incomplete screening in most studies, multivessel FMD was identified in 19.1% of patients (US Registry 55.1%; FEIRI 57.4%), and aneurysms and dissections in 15.3% and 1.7%, respectively (US Registry 22.7%, 28.1%; FEIRI 21.6%, 5.6%). Conversely, the proportion of associated mid-aortic syndrome (MAS) in children with FMD was only 6.3%. In exploratory ethnicity-stratified analyses, the pooled female proportion was 43.5% in Asian children vs. 58.2% in Caucasian children and the prevalence of multifocal FMD was 21.8% vs. 37.9%, respectively. Conclusions: Compared with adult FMD patients, children/adolescents with FMD are characterized by a lower proportion of females and a higher proportion of focal FMD, both in Asian and Caucasian populations. While associated MAS appears to be less frequent than previously thought, multivessel involvement and aneurysms were identified at non-negligible frequencies, suggesting the interest of a systematic arterial exploration in children with FMD, as recommended in adults.