Germline heterozygous mutations in the genes encoding core PRC2 members (EZH2, EED and SUZ12), NSD1 and DNMT3A have been implicated in a triad of highly phenotypically related human developmental disorders: Weaver syndrome, Sotos syndrome and Tatton-Brown–Rahman syndrome, respectively (summarised in Table 2). This evidence concerns the gene DNMT3A and Tatton-Brown-Rahman overgrowth syndrome.