ObjectiveTo describe phenotypes and estimate the prevalence of familial cases of renal artery fibromuscular dysplasia (FMD).Patients and settingOne hundred and four unrelated hypertensive patients (94 women) with renal artery fibromuscular dysplasia documented on angiography and classified as having multifocal or unifocal lesions. Familial cases were defined as those with angiographic evidence of renal artery FMD in at least one sibling.ResultsEighty-one patients had multifocal and 16 had unifocal FMD. Both types of stenosis were present in seven patients. Fifty-four patients had bilateral FMD, including the seven patients with both unifocal and multifocal lesions. The 16 patients with unifocal FMD were younger, more likely to be men, and more commonly had unilateral stenoses, stenoses exceeding 75% and a small ischemic kidney than the 81 patients with multifocal lesions. Eleven cases were identified as familial on the basis of FMD having been documented in at least one sibling (eight sibling pairs and three trios). All probands were women and exhibited multifocal lesions. FMD was more often bilateral in familial than it was in apparently sporadic cases.ConclusionsMultifocal FMD was mostly found in women and unifocal FMD in young men with more severe stenosis and kidney ischemia. The documented prevalence of familial cases was 11% in this series, the true prevalence being probably higher because only a few siblings were examined by angiography. Familial cases all exhibited the multifocal type and were more commonly bilateral than were sporadic cases.