SETD1B is one of the six H3K4 methyltransferases present in mammals, and remarkably loss of function of each is associated with human disease (KMT2A: Wiedemann–Steiner syndrome [OMIM 605130]; KMT2B: early-onset dystonia [OMIM 617284]; KMT2C: Kleefstra syndrome type 2 [OMIM 617768]; KMT2D: Kabuki syndrome [OMIM 147920]), with the latest additions to this list being SETD1A and SETD1B (also known as KMT2F and KMT2G, respectively). Here, KMT2D is linked to Kabuki syndrome.