To explore the phenotype and molecular genetic features of spinocerebellar ataxia type 2 (SCA2) cases with ATXN2 intermediate-length CAG-repeat expansion.

Fragment analysis by capillary electrophoresis was performed to detect the dynamic mutations in the samples of the probands in 1 383 pedigrees with autosomal dominant inherited ataxia in Research Center for Motor Disorders and Neurogenetic Diseases, Department of Neurology, China-Japan Friendship Hospital from 2005 to 2018. The clinical and genetic features of individuals carrying the ATXN2 intermediate-length CAG-repeat expansion were carefully analyzed.

Two hundred and three individuals (including the probands and members of their families) in 163 families carried the expanded CAG repeats in ATXN2 gene, among which 107 individuals in 93 families carried the intermediate-length CAG-repeats. Within 20 parent-child pairs, the CAG repeats increased 0-28 copies in 16 pairs with paternal inheritance, and 0-4 copies in 4 pairs with maternal inheritance.

For suspected SCA2 cases, ATXN2 gene testing should be performed on the parental members and adult offspring members in the family. Dynamic mutations testing is essential to identify the individuals with ATXN2 intermediate-length repeat expansion, which is very important for genetic counseling.

Spinocerebellar ataxias; Pedigree; Mutation; ATXN2 gene; Intermediate-length repeat expansion