Tatton-Brown–Rahman syndrome (TBRS) is caused by a mutation in DNMT3A, a gene that is also associated with Sotos syndrome, which is caused by haploinsufficiency of NSD1, an HMT that catalyzes the demethylation of histone H3 at K36 (H3K36m22). Here, DNMT3A is linked to Tatton-Brown-Rahman overgrowth syndrome.