C9orf72 and amyotrophic lateral sclerosis: We confirmed the association between C9orf72 and ATXN2 and ALS susceptibility, with the best thresholds aligning with those previously reported.27,44,57,69,70 Progression analysis validated C9orf72 as a modifier of ALS survival and age at onset, again with thresholds consistent with earlier findings.71-73 We found no compelling evidence that other STR loci are associated with ALS, even when considering repeat lengths shorter or longer than established pathogenic thresholds.