Nonsyndromic hydrocephalus includes the classical X‐linked type associated with mutations in L1CAM (MIM 307000) and autosomal recessive hydrocephalus related to the gene CCDC88C (HYC1, MIM 236600), MPDZ (HYC2, MIM 615219), and WDR81 (HYC3, MIM 617967). The gene discussed is MPDZ; the disease is Hydrocephalus.