Polyglutamine Ataxias in Denmark: Incidence and Relative Frequencies of SCA1, 2, 3, 6, 7, 17 and DRPLA in a Nationwide Cohort

Polyglutamine ataxias are autosomal dominantly inherited neurodegenerative disorders in which the molecular aetiology is an expanded CAG glutamine-encoding repeat in the causative genes. At present, there is no effective treatment, but there are several ongoing trials addressing polyglutamine disorders increasing the need of knowledge about prevalence and relative frequencies of the different subtypes. To identify all individuals with genetically confirmed polyglutamine ataxia in Denmark, determine frequency of subtypes and estimate the incidences. Retrospective data on all clinical tests performed on polyglutamine ataxias in Denmark during the last 15 years. 215 individuals with alleles in the full penetrant pathogenic range of polyglutamine ataxia genes were identified. The most frequent polyglutamine ataxia in Denmark was SCA6 which accounts for 42% of the identified individuals, followed by SCA2 and SCA3 which both account for approximately 20% each. Incidence rates were calculated. The study reveals the subtype distribution and incidence of polyglutamine ataxias in Denmark, priming the Danish cohort for future clinical trials as developments in the treatment of polyglutamine ataxia advances.