In individuals with MICPCH or X-linked intellectual disability (XLID), over 100 investigations have documented a variety of CASK variants, including missense variants (LaConte et al., 2018), intragenic duplications (Hayashi et al., 2012), splice site variants (Dunn et al., 2017), rearrangements, and deletion-insertion variants (Saitsu et al., 2012; Moog et al., 2015; Hayashi et al., 2017). Here, CASK is linked to X-linked intellectual disability.