ZDHHC9 and cask-related x-linked intellectual disability: Here, we studied a group of individuals with mutations in ZDHHC9, a rare recurrent cause of X‐linked intellectual disability (XLID; Han et al., 2017; Raymond et al., 2007; Schirwani, Wakeling, Smith, Study, & Balasubramanian, 2018; Masurel‐Paulet et al 2014).