Identifying the KAT6B Mutation via Diagnostic Exome Sequencing to Diagnose Say-Barber-Biesecker-Young-Simpson Syndrome in Three Generations of a Family

Diagnostic exome sequencing (DES) is a powerful tool to analyze the pathogenic variants leading to development delay (DD) and intellectual disability (ID). Recently, heterozygous de novo mutation of the histone acetyltransferase encoding gene KAT6B has been recognized as causing a syndrome with congenital anomalies and intellectual disability, namely Say-Barber-Biesecker-Young-Simpson (SBBYS) syndrome. Here we report a case of SBBYS syndrome in a third generation Korean family affected with a missense mutation in KAT6B, c.2292C>T p.(His767Tyr) identified by DES. This is the first confirmed familial inherited mutation of the KAT6B reported worldwide. Our case emphasizes again the importance of basic physical examination and taking a family history. Furthermore, advances in genetic diagnostic tools are becoming key to identifying the etiology of DD and ID. This allows a physiatrist to predict the disease's clinical evolution with relative certainty, and offer an appropriate rehabilitation plan for patients.