KAT6B and blepharophimosis - intellectual disability syndrome, SBBYS type: Heterozygous de novo mutations in the KAT6B gene, which encodes the histone acetyltransferase, can cause two syndromes with mental retardation and congenital abnormalities, known as Genitopatellar syndrome (GPS; OMIM #606170) and Say–Barber–Biesecker–Young–Simpson syndrome (SBBYSS, OMIM #603736) [1].