ATXN2 and amyotrophic lateral sclerosis: In several back-to-back reports, ATXN2 intermediate alleles associated with ALS have been defined differently across the populations, e.g. in the USA ≥27 CAG [2], in Europe ≥30 CAG [3], in Belgium and Netherland ≥32 CAG [5], suggesting a range of at-risk alleles with 27–30 CAG and alleles causing the disease with ≥31 CAG.