The spinocerebellar ataxias (SCAs) are a group of autosomal dominantly inherited progressive ataxia disorders. More than 40 genetically different SCAs have been defined that mostly follow the nomenclature of SCA followed by a number, except DRPLA. The most common – SCA1, SCA2, SCA3 and SCA6, which together affect more than half of all families with a history of SCA – are caused by translated CAG repeat expansion mutations that code for an elongated polyglutamine tract within the respective proteins. Other SCAs are caused by non-repeat or by non-translated repeat mutations that affect a variety of different genes.
SCAs have a worldwide distribution, however with variable prevalence rates reported across the world. Despite the large heterogeneity of the various SCAs, people with SCA and their families are facing similar problems. Once started, ataxia takes a relentlessly progressive course leading to disability and often premature death. Ataxia is frequently accompanied by non-ataxia symptoms which considerably impact quality of life. Currently, there is no cure for any SCA. In fact, there are not even symptomatic medical treatments so that management of SCA patients has to rely on physical and speech therapy.