Progress in next-generation sequencing has led to an explosion of novel genes and phenotypes of autosomal recessive cerebellar ataxias (ARCAs) in the last decade, with >170 recessive conditions manifesting with ataxia identified.1 With large-scale natural history and mechanistic treatment trials on the horizon for many ARCAs, up-to-date knowledge is required not only on relative frequencies but also on real-world age and disease severity distributions as key information for trial design planning and recruitment. In this multicenter study, we provide data on the relative frequency of ARCAs in Europe, delineate the spectrum of age at disease onset, and present real-world data on disease severity distributions of patients with ARCA that help to inform future trial planning
