Spinocerebellar ataxia type 17 (SCA17) is a rare subtype of type I autosomal dominant cerebellar ataxia (ADCA type I; see this term). It is characterized by a variable clinical picture which can include dementia, psychiatric disorders, parkinsonism, dystonia, chorea, spasticity, and epilepsy.
Worldwide prevalence is unknown. Local prevalence is 0.47 per 1,000,000 in the Japanese population and 0.16 per 100,000 in North-East England. Fewer than 100 families have been reported to date.
Clinical features overlap with many neurodegenerative syndromes and specifically, Huntington disease (see this term).
SCA17 is caused by a CAG repeat expansion in the TATA box-binding protein gene TBP (6q27).
Prognosis is poor. More than 60% of patients present with dysphagia which frequently results in aspiration and death. Mean disease duration is less than 18 years and a few patients live beyond 60 years of age.