RAB18 and microcephaly: Variants in multiple genes regulating endosomal trafficking and/or fusion of secretory vesicles [such as SMPD4, WDFY3, TRAPPC4, RAB18, VPS13B, EXOC7, EXOC8, VPS11 (Coulter et al. 2020; Le Duc et al. 2019; Magini et al. 2019; Momtazmanesh et al. 2020; Van Bergen et al. 2020)], have been associated with the occurrence of microcephaly, cerebral atrophy, and neurodevelopmental delay.