Dominant spinocerebellar ataxias are a rare clinically and genetically heterogeneous group of neurodegenerative disorders. They are characterized by progressive cerebellar ataxia resulting in unsteady gait, clumsiness, dysarthria, and swallowing difficulty. The onset of symptoms is usually in the third or fourth decade of life; however, more subtle clinical manifestations can start in early childhood. Spinocerebellar ataxia type 5, a dominant spinocerebellar ataxia associated with mutations involving β-III spectrin (SPTBN2), has been described in 3 families. It typically consists of a slowly progressive spinocerebellar ataxia with onset in the third decade. The authors present the first case of infantile-onset spinocerebellar ataxia associated with a novel SPTBN2 mutation (transition C>T at nucleotide position 1438), the proband having a much more severe phenotype with global developmental delay, hypotonia, tremor, nystagmus, and facial myokymia.