Megalencephaly-polymicrogyria-polydactyly-hydrocephalus (MPPH) syndrome is caused by mutations, in order of frequency, of either PIK3R2, AKT3, or CCND2 genes with consequent activation of the PI3K-AKT-mTOR pathway (172). The gene discussed is AKT3; the disease is Megalencephaly - polymicrogyria - postaxial polydactyly - hydrocephalus.