A CAG repeat expansion in the TATA-box-binding protein (TBP) gene on chromosome 6 has been identified as the cause of SCA17 in some familial and sporadic cases, resulting in cerebellar ataxia and followed by dementia, parkinsonism, and dystonia, with onset in childhood and adulthood [89,90]. The gene discussed is TBP; the disease is cerebellar ataxia.