Homozygous NUS1 mutations in this gene were previously described to cause congenital disorder of glycosylation type Iaa (CDG1AA, OMIM 617082) (30), while rare heterozygous mutations were reported in two cases with autosomal dominant mental retardation-55 with seizures (MRD55, OMIM 617831) (31). Here, NUS1 is linked to intellectual disability, autosomal dominant 55, with seizures.