SACS and Charlevoix-Saguenay spastic ataxia: This is likely due to the fact that this variant localizes at the very 3′ end of the SACS gene, while in our previous report the truncating variants were located further upstream.7 Since the p.Arg4378X is expected to result in the loss of part of the DnaJ domain and of the HEPN domain, this finding raises the intriguing hypothesis that both these domains are central in ARSACS pathogenesis.