NELL2 and Intellectual disability: Genomic and clinical delineation has enabled the dissection of this region, allowing for the identification of intellectual disability and craniofacial candidate genes YAF2 (MIM 607534) and PRICKLE1 (MIM 608500), while haploinsufficiency of NELL2 (MIM 602320) and DBX2 are suggested to be the cause of psychomotor delay and motor delay, respectively [13,14,15].