Mutations in RAB39B gene are associated with a variety of neurological disorders including X-linked intellectual disability (XLID), autism, epilepsy, macrocephaly and early-onset Parkinson’s disease (EOPD) (Giannandrea et al., 2010; Wilson et al., 2014; Mata et al., 2015; Shi et al., 2016; Woodbury-Smith et al., 2017; Gao et al., 2020). Here, RAB39B is linked to X-linked intellectual disability.