SACS and Charlevoix-Saguenay spastic ataxia: The p.Arg4378X variant has been already reported in trans with another pathogenic variant in the SACS gene (c.1178_1181delAT; p.Leu393Cysfs*17) in a patient with ARSACS.14 We further validated the pathogenicity of this variant by assaying vimentin remodelling by immunofluorescence in primary fibroblasts from PN7 and comparing to PN6 and healthy controls.