To estimate the prevalence of the main spinocerebellar ataxias in South America.

Spinocerebellar ataxias (SCAs) are autosomal dominant neurodegenerative disorders characterized by cerebellar ataxia with variable extracerebellar symptoms. More than 40 SCAs have been reported, and their prevalence varies significantly across different regions.

We conducted a systematic search in PubMed, EMBASE, Scopus, and WOS, combining the terms “autosomal dominant cerebellar ataxia”, “spinocerebellar ataxia”, “epidemiolog*”, “etiolog*”, “prevalence”, “Latin America” and “ATXN*”, “SCA*”, “SPTBN2”, “CACNA1A/G”, “TTBK2”, “PPP2R2B”, “ITPR*”, “FGF*”, “TTBK”, “KCN*” for SCA genes, from inception to 09/2023, without language restrictions. We included studies where the prevalence of one or more SCA types was reported independently by country. We conducted a proportions meta-analysis and a random effect method to estimate pooled rates.

Of 123 records, 11 studies were included, comprising 3 606 individuals with clinical diagnosis of SCA. 5 studies were performed in Brazil, 2 in Peru, 1 in Argentina, 1 in Cuba, 1 in Venezuela, and 1 in Chile. In our meta-analysis we found that SCA2 was the most prevalent type (24%, 95%CI 8–52%), followed by MJD/SCA3 (14%, 95%CI 5–32%) and SCA10 (13%, 95%CI 4–34%). Brazil had the highest prevalence of SCA3, Argentina and Cuba of SCA2, and Peru of SCA10. Other reported SCAs were SCA7 (7%, 95%CI 3–18%), SCA1 (7%, 95% CI3-13%), DRPLA (2%, 95% CI 1–7%), and SCA6 (2%, 95% CI 1–5%). There were three isolated cases of SCA28, SCA36, SCA48 reported in Argentina, 8 cases of SCA27b in Brazil, and an important proportion of SCAs of unknown genotype (17%, 95% CI 12–24%).  

Among individuals with genetically confirmed spinocerebellar ataxia, SCA2, MJD/SCA3, and SCA10 are the most prevalent types in South America, with variable geographic differences across countries. Importantly, the accuracy of our results is affected by the significant lack of prevalence studies in most countries.