An OGT Missense Variant With Impaired Enzyme Activity in a Child With Severe Developmental Delay and Hepatoblastoma

O-GlcNAc transferase (OGT) and its antagonist O-GlcNAcase (OGA) regulate protein O-GlcNAcylation, a highly conserved post-translational modification involved in metabolic sensing. Pathogenic variants in the OGT gene cause an X-linked congenital disorder of glycosylation (OGT-CDG) presenting developmental delay, hypotonia, intellectual disability, and dysmorphic features. Here, we report on a child with developmental delay, hypotonia, and dysmorphic features who was found to carry a hemizygous novel OGT variant.