ATXN2 and amyotrophic lateral sclerosis: ATXN2 polyQ intermediate number of repeats were first recognised as a risk factor for ALS in 2010 in a cohort of US patients (using a cut-off≥27)16 and subsequently confirmed in populations of different ethnic origin,3 with the only exception of South Africans.17 Although a length of 27–33 polyQ was initially considered significantly associated with ALS, later studies have shown that the cut-off is≥31 polyQ repeats.