PRDM9 and Intellectual disability: However, haploinsufficiency of several histone methyltransferase genes is known to result in syndromic intellectual disability exemplified by: MLL2 (myeloid/lymphoid or mixed-lineage leukemia 2) in Kabuki syndrome (MIM 147920) and EHMT1 (Euchromatic Histone Methyltransferase 1) in Kleefstra syndrome (MIM 610253).