Novel De Novo KMT2A Missense Variant in a Boy with Wiedemann-Steiner Syndrome

Wiedemann-Steiner syndrome (WDSTS) is a rare autosomal dominant disorder characterized by global developmental delay, short stature, and distinctive facial dysmorphism, caused by heterozygous pathogenic variants in KMT2A. We report a 1-year-old boy presenting with global developmental delay, short stature, and a characteristic facial gestalt consistent with WDSTS; hypertrichosis, hypertelorism, epicanthus, downslanted palbepral fissures, short depressed nose and micrognathia. Whole-exome sequencing identified a novel de novo heterozygous missense variant in KMT2A (NM_001197104.1:c.3580T>C; p.(Cys1194Arg)), not present in either parent, predicted pathogenic by in silico analysis. This case broadens the understanding of WDSTS’s clinical presentation and genetic basis.