Spinocerebellar ataxias in Southern Brazil: Genotypic and phenotypic evaluation of 213 families

Objectives: To describe and correlate the genotype and phenotype of patients diagnosed with SCAs in southern of Brazil. Patients and methods: Data were collected from the records of our ataxia outpatient clinic. We included 460 patients from 213 families, who were divided into four groups: SCA3, SCA10, Other SCAs and Undetermined. Results: The most frequent type was SCA3 (45.7%), followed by SCA10 (18.3%), SCA2 (6.5%), SCA1 (4.3%), SCA7 (1.8%), and SCA6 (0.65%). The Undetermined group represented 22.8% of all patients. We observed a high frequency of SCA10 when compared to data from other studies, which can be explained by a founder effect in our region. Statistically significant differences were found for several symptoms when comparing SCA groups, especially lid retraction (p < 0.001), ophthalmoplegia (p < 0.001), visual loss (p < 0.001) and slow saccades (p < 0.001) which may help clinically differentiate SCAs and allow neurologists to request the right confirmatory genetic test and define prognosis. Also, the prevalence of epilepsy in SCA10 patients was lower than usual (4.8%), suggesting a genetic variation of the disease. Conclusion: Although SCA3 remains the most common, we observed a high frequency of SCA10 in our region. In addition, some symptoms and signs might help differentiate the SCAs.