EP300 and Rubinstein-Taybi syndrome: RSTS is caused by monoallelic pathogenic variants in either CREBBP (RSTS1) or EP300 (RSTS2) genes [3,4], which encode the paralog CBP and p300 chromatin modifiers acting as transcriptional coactivators and histone and non-histone lysine (K) acetyltransferases (HATs or KATs) [5].