ATXN3 and autosomal dominant cerebellar ataxia: SCA27B comprised 16% of all SCA index patients representing the second most common SCA, after SCA3 with 19%.15 The first study on the US population with undiagnosed ataxia of predominantly White individuals, recruited from five academic centres, identified 55 out of 732 patients (7.5%) with the GAA repeat expansion.24 The prevalence in Brazil is 9%, while the prevalence among South-Asian and East-Asian populations is significantly lower, as evidenced by rates observed in India (1.8%), China (1.3%) and Japan (1.2%).18,19,21,30