The cognitive deficits and epilepsy that are hallmarks of ZDHHC9-associated XLID are often ascribed to malformations of neocortical gray matter (Stevenson et al., 2013; Guerrini and Dobyns, 2014; Lim and Crino, 2013; Zhang et al., 2010; Juric-Sekhar and Hevner, 2019). Here, ZDHHC9 is linked to cask-related x-linked intellectual disability.