Due to the potential discrepant pathogenesis between C9orf72 HRE with reduced expression and the intermediate length of C9orf72 with increased expression, the suggested role of ATXN2 in C9orf72 HRE carriers should be re-evaluated in ALS patients without C9orf72 HRE. Here, C9orf72 is linked to amyotrophic lateral sclerosis.