Spinocerebellar ataxia type 17 (SCA17) is an autosomal dominant cerebellar ataxia characterized by cerebellar ataxia and dementia with sometimes extensive variability in phenotypes such as Huntington’s disease-like symptoms (HDL), caused by abnormal expansion of a CAG/CAA repeat encoding a polyglutamine (polyQ) tract in the TATA-box binding protein (TBP) gene [1]. The gene discussed is TBP; the disease is dementia.