In addition to ALS-specific variants, two novel pathogenic missense mutations were found in NEFH and ALS2 genes in the ALS patient and the SCA1-MN member (IV-15) but absents in the SCA1 patient without MN signs (IV-26), suggesting these variants or their combination may contribute to the MN phenotypic heterogeneity observed amongst family members (Table 1). This evidence concerns the gene ATXN1 and amyotrophic lateral sclerosis.