HDAC8 and KBG syndrome: Whereas for NIPBL and RAD21 patients, KBG syndrome was the second most common diagnosis (top-five rank), 54.5% (18/33) and 66,7% (2/3), Rubinstein–Taybi syndrome appeared most frequently in SMC1A and HDAC8 patients, 50.0% (4/8) and 80.0% (4/5), respectively (Figure 2) (Supplementary Table S1).