The diagnosis of Spastic Paraplegia 50 (SPG50, MIM 612936), Cerebral creatine deficiency syndrome 1 (MIM 300352, CCDS1), as well as Mental retardation, autosomal dominant 31 (MIM 616158, MRD31), would not be possible without the application of next‐generation sequencing. Here, SLC6A8 is linked to cerebral creatine deficiency syndrome.