We validated the known pleiotropic association of C9orf72 and ATXN2 with ALS.27,44,69,70 While ATXN1 premutations were strongly associated with ALS, the association did not reach significance as reported previously, despite including overlapping data in both studies.33 This may be attributed to sample size differences. Here, C9orf72 is linked to amyotrophic lateral sclerosis.