ESPE Abstracts

Say-Barber-Biesecker-Young-Simpson syndrome (SBBYSS) is a rare and clinical well-described disease caused by de novo heterozygous mutations in KAT6B gene. Genitopatellar syndrome (GS) is also caused by the mutations of gene KAT6B and shares some common clinical symptoms with SBBYSS. The phenotypic spectrum caused by KAT6B is very broad that some patients cannot be classified as SBBYSS or GS. Herein, we report one de novo heterozygous KAT6B truncating variants c.5124delC (p.L1709Sfs*5) in a 5-year-old girl presenting with severe blepharophimosis, a bulbous nasal tip, dental anomalies, abnormally long thumbs and great toes, congenital cardiac defects, congenital hypothyroidism, and significantly impaired speech. The c.5124delC (p.L1709Sfs*5) variant affects to exon 18, where is the Ser rich region. The clinical and genetic charaterizaiton could contribute to the understanding of SBBYSS.