TRAPPC9 and microcephaly: TRAPPC9 deficiency results in severe intellectual disability usually accompanied by absent or delayed speech, and microcephaly, with varied reports of stereotypic movements and dysmorphic features (Abbasi et al., 2017; Abou Jamra et al., 2011; Duerinckx et al., 2018; Giorgio et al., 2016; Hnoonual et al., 2019; Kakar et al., 2012; Koifman et al., 2010; Marangi et al., 2013; Mir et al., 2009; Mochida et al., 2009; Mortreux et al., 2018; Najmabadi et al., 2007; Philippe et al., 2009).