LAUSR

A 78-year-old woman (Ms J) presented for evaluation of fibromuscular dysplasia (FMD) after an episode of left amaurosis fugax. She had been followed with annual carotid duplex ultrasound imaging for reported bilateral carotid artery stenosis over the past 5 years. During her initial visit, she was accompanied by her identical twin sister (Ms L), who interestingly had also been diagnosed with bilateral ‘carotid artery stenosis’ after being found to have cervical bruits. Both sisters (Panel A) reported a history of hypertension and hyperlipidemia; in addition, both endorsed symptomatic pulsatile tinnitus, a common symptom of carotid FMD. Subsequent computed tomography angiographic (CTA) imaging revealed multifocal FMD in both twins. Ms J had involvement in the bilateral internal carotid arteries (ICA) (Panel B; reformatted CTA images), bilateral vertebral arteries, and bilateral renal arteries, as well as two small intracranial ICA aneurysms. Ms L had involvement in the bilateral ICAs (Panel C; reformatted CTA images) and right renal artery, as well as a small splenic artery aneurysm. FMD is a nonatherosclerotic arterial disease seen primarily in women.1 The involved vessels (typically the internal carotid and renal arteries) have a notable ‘string of beads’ appearance in classic multifocal FMD. Symptoms may include pulsatile tinnitus, hypertension, and ischemic phenomena (as seen in our patient), along with arterial aneurysm and dissection. Little is known about the pathogenesis of the disease, and cases are not typically familial. In the US Registry for FMD, only 7.3% of patients reported an affected first or second degree relative.2 Identical twins with carotid and renal FMD have been previously reported.3 Recently, genome-wide association studies have identified a variant of the phosphatase and actin regulator 1 gene (PHACTR1) as a potential susceptibility locus for multifocal FMD.4 Our case of multifocal FMD in identical twin sisters further illustrates the likelihood of an underlying genetic component to the development of FMD and supports the need for additional research, including studies of affected families. Seeing double: Multifocal fibromuscular dysplasia in identical twin sisters