ARHGEF9 and cask-related x-linked intellectual disability: This strongly suggested that one of the novel missense variants identified in the established XLID genes ARHGEF9 (Harvey et al., 2004; Marco et al., 2008; Kalscheuer et al., 2009; Lesca et al., 2011; Shimojima et al., 2011; Lemke et al., 2012; de Ligt et al., 2012; Long et al., 2016; Alber et al., 2017; Klein et al., 2017; Wang et al., 2018) and CCDC22 (Voineagu et al., 2012; Kolanczyk et al., 2015) or a combination of both could be responsible for XLID in this family.