Preferential FMN vulnerability has been observed in SOD1 [15–17], TDP-43 [18], FUS [19] and C9ORF72 [20] mutant mice, with limb-onset ALS accounting for ~ 70% of human pathology [21], suggesting that preferential FMN vulnerability in ALS is conserved across species. Here, SOD1 is linked to amyotrophic lateral sclerosis.