KAT6B and genitopatellar syndrome: Furthermore, heterozygous loss-of-function variants of histone acetyltransferase KAT6B causes two different genetic disorders, Genitopatellar syndrome and SBBYSS syndrome (23), both of which are characterized by patellar hypoplasia, and a variety of growth phenotype that may include microcephaly and postnatal growth retardation, which has been proposed to be mediated by regulation of RUNX2 expression by KAT6B (24).