Kabuki Syndrome: Case Report of Severe Prenatal Midface Hypoplasia (Binder Phenotype), due to a Novel Variant in the <i>KMT2D</i> Gene

Kabuki syndrome (KS) is a rare genetic disorder with a prevalence of 1/86,000-1/32,000. Pathogenic variants in the KMT2D and KDM6A genes are responsible for the majority of KS cases and are inherited in an autosomal dominant and X-linked manner, respectively. Despite KS being genetically pleiotropic, specific phenotypic features, such as hypotonia, developmental disorders, mental retardation, dermatoglyphic and facial abnormalities, are widely manifested among patients with KS. Only few prenatal findings have been associated with KS so far. This report highlights an interesting and infrequent case of a neonate with severe midface hypoplasia and multiple congenital anomalies, which were noted on the 2nd trimester antenatal scan. The degree of hypoplasia was indicative of chondrodysplasia punctata, but there was no relevant pregnancy history or other features of a skeletal dysplasia. The pregnancy was complicated by preterm premature rupture of membranes. The neonate was born at 27 weeks of gestation and died 16 days later, due to complications of prematurity. Whole exome sequencing identified a novel de novo KMT2D pathogenic variant. Although midface hypoplasia has been previously reported in individuals with KS, the severity noted in the index individual is an unusual feature of the syndrome.