Human SIRH11/ZCCHC16 is located on Xq23, where several X-linked intellectual disability (XLID) genes have been mapped, such as PRPS1 (–5 Mb from SIRH11/ZCCHC16), ACSL4 (–2.5 Mb), PAK3 (–1 Mb), DCX (–1 Mb), AGTR2 (+4 Mb), LAMP2 (+8 Mb) and GRIA3 (+11 Mb). This evidence concerns the gene RTL4 and cask-related x-linked intellectual disability.