Late-Onset Spinocerebellar Ataxia 2 with Only 32 CAG Repeats

Spinocerebellar ataxia type 2 (SCA2) is an autosomal dominant disorder caused by CAG trinucleotide repeat expansion in the ATXN2 gene. Only a few SCA2 patients with intermediate alleles (32-34 repeats) have been reported. Herein, we describe a patient confirmed to have SCA2 with 32 CAG repeats in ATXN2. A 66-year-old man presented with progressive unsteadiness and dysarthria for several months. Brain magnetic resonance imaging (MRI) showed diffuse cerebellar atrophy, and genetic analysis confirmed 32/22 CAG repeats in ATXN2. CAG repeat counts in ATXN2 are typically approximately 22 in 90% of the general population, with very low polymorphism. These findings suggest that even a minimal expansion beyond the normal upper limit may be sufficient to cause disease, albeit with a markedly delayed onset.