KAT6B and Cognitive impairment: Heterozygous mutations in the MYST family histone lysine acetyltransferase gene, KAT6B (MYST4/QKF/MORF) cause the Say-Barber-Biesecker-Young-Simpson variant of Ohdo syndrome, Genitopatellar syndrome, and similar disorders (Clayton-Smith et al, 2011; Campeau et al, 2012; Simpson et al, 2012), defined by a global development delay and cognitive impairment.