Rare but Instructive: Pediatric-Onset Spinocerebellar Ataxia Type 2 and Its Clinical and Genetic Insights.

Spinocerebellar ataxia type 2 (SCA2) is an autosomal dominant neurodegenerative disorder caused by CAG trinucleotide repeat expansion in the ATXN2 gene. While typically adult-onset, pediatric cases are rare and exhibit distinct clinical features. Here, we report two pediatric-onset SCA2 cases. A 7-year-old boy with involuntary movements, developmental delay, and 58 CAG repeats, and a 16-year-old boy with tremors and gait instability carrying 44 repeats. Both showed cerebellar atrophy on MRI. A literature review of 22 genetically confirmed pediatric SCA2 cases revealed a strong inverse correlation between CAG repeat length and age at onset (R2 = 0.6131, P < 0.00001). Common features included developmental delay, hypotonia, epilepsy, and dystonia, with 79% of cases showing paternal inheritance. These findings underscore the importance of considering SCA2 in children with atypical neurodevelopmental symptoms and highlight the role of genetic anticipation in early-onset cases.