KLHL15 (MIM #300980), localized on chromosome Xp22.11, was recently identified as a gene that causes X-linked intellectual disability (XLID, MIM #300982) and functions as an adapter for cullin3 (Cul3)-based E3 ubiquitin ligases that target specific substrates of the ubiquitin‒proteasome system2–4. Here, KLHL15 is linked to cask-related x-linked intellectual disability.