Frequency of GAA-FGF14 Ataxia in a Large Cohort of Brazilian Patients With Unsolved Adult-Onset Cerebellar Ataxia

OBJECTIVES: 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. METHODS: 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. RESULTS: 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%). DISCUSSION: 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.