CCND2 GoF variants have been associated with megalencephaly-polymicrogyria-polydactyly-hydrocephalus syndrome 3 (MPPH3, OMIM#615938), a developmental brain disorder characterized by megalencephaly, bilateral perisylvian polymicrogyria, and postaxial polydactyly (28). This evidence concerns the gene CCND2 and megalencephaly.