Intronic FGF14 GAA repeat expansions have recently been found to be a common cause of hereditary ataxia (GAA-FGF14 ataxia; SCA27B). The global epidemiology and regional prevalence of this newly reported disorder remain to be established. In this study, we investigated the frequency of GAA-FGF14 ataxia in a large cohort of Brazilian patients with unsolved adult-onset ataxia.

We recruited 93 index patients with genetically unsolved adult-onset ataxia despite extensive genetic investigation and genotyped the FGF14 repeat locus. Patients were recruited across 4 different regions of Brazil.

Of the 93 index patients, 8 (9%) carried an FGF14 (GAA)_≥250 expansion. The expansion was also identified in 1 affected relative. Seven patients were of European descent, 1 was of African descent, and 1was of admixed American ancestry. One patient carrying a (GAA)₃₇₆ expansion developed ataxia at age 28 years, confirming that GAA-FGF14 ataxia can occur before the age of 30 years. One patient displayed episodic symptoms, while none had downbeat nystagmus. Cerebellar atrophy was observed on brain MRI in 7 of 8 patients (87%).

Our results suggest that GAA-FGF14 ataxia is a common cause of adult-onset ataxia in the Brazilian population, although larger studies are needed to fully define its epidemiology.

最近发现内含子FGF14 GAA 重复扩增是遗传性共济失调（GAA- FGF14共济失调；SCA27B）的常见原因。这种新报告疾病的全球流行病学和区域患病率仍有待确定。在这项研究中，我们调查了一大群患有未解决的成人发病性共济失调的巴西患者中GAA- FGF14共济失调的频率。

尽管进行了广泛的基因调查，我们还是招募了 93 名患有遗传未解决的成人发病性共济失调的指标患者，并对FGF14重复基因座进行了基因分型。在巴西 4 个不同地区招募患者。

在 93 名指数患者中，8 名 (9%) 携带FGF14 (GAA) _≥250扩增。在 1 名受影响的亲属中也发现了这种扩张。7名患者是欧洲血统，1名是非洲血统，1名是美国混血儿。一名携带 (GAA) ₃₇₆扩展的患者在 28 岁时出现共济失调，证实 GAA- FGF14共济失调可能在 30 岁之前发生。一名患者表现出阵发性症状，但没有人出现悲观的眼球震颤。8 名患者中有 7 名 (87%) 的脑部 MRI 观察到小脑萎缩。

我们的结果表明，GAA- FGF14共济失调是巴西人群中成人发病的共济失调的常见原因，尽管需要更大规模的研究来完全确定其流行病学。