Association of Multifocal Fibromuscular Dysplasia in Elderly Patients With a More Benign Clinical Phenotype: Data From the US Registry for Fibromuscular Dysplasia.

Importance: Fibromuscular dysplasia (FMD) is a nonatherosclerotic arterial disease that predominately affects women and is most commonly diagnosed in middle age. The natural history of FMD among patients diagnosed at an older age is not well understood.

Objective: To examine the differences in clinical presentation, arterial bed involvement, vascular events, and need for vascular procedures between younger and older patients with FMD.

Design, Setting, and Participants: Analysis of baseline data for patients enrolled in the US Registry for FMD as of December 15, 2016, at referral centers participating in the US Registry for FMD. Patients 18 years and older at the time of enrollment and those with only confirmed multifocal (string of beads type) FMD were included. Patients were categorized according to age at the time of diagnosis (≥65 years vs <65 years).

Main Outcomes and Measures: Prevalence of specific symptoms, vascular events, and prior vascular procedures at the time of enrollment in the registry.

Results: A total of 1016 patients were included in the analysis, of whom, 170 (16.7%) were 65 years or older at the time of diagnosis. Older patients with FMD were more likely to be asymptomatic at the time of diagnosis (4.2% vs 1.4%; P = .02). Headache and pulsatile tinnitus, both common manifestations of FMD, were less common in older patients (40.5% vs 69.1%; P < .001 and 30% vs 44.6%; P < .001, respectively). Extracranial carotid arteries were more commonly involved in patients 65 years or older at time of diagnosis (87% vs 79.4%; P = .03). There was no difference in prevalence of renal artery involvement, number of arterial beds involved, or diagnosis of any aneurysm. Patients 65 years or older were less likely to have had a major vascular event (37.1% vs 46.1%; P = .03) and fewer had undergone a therapeutic vascular procedure (18.5% vs 33.1%; P < .001).

Conclusions and Relevance: In the US Registry for FMD, patients 65 years or older at the time of diagnosis of multifocal FMD were more likely to be asymptomatic, had lower prevalence of major vascular events, and had undergone fewer therapeutic vascular procedures than younger patients. Patients with multifocal FMD diagnosed at an older age may have a more benign phenotype and fewer symptoms.