KARS1 and Spastic tetraparesis: The only KARS mutation presents in two unrelated families was the p.Arg505His, identified in homozygosity in patient A and in compound heterozygosity with p.Pro533Ser in Pts 21–22; all these three individuals were characterized by leukodystrophy and hearing problems but the MRI features were not identical and other clinical symptoms were different (e.g. visual impairment and spastic tetraparesis were observed in patient A but not in the two siblings).