We report a new patient with refractory epilepsy associated with a novel pathogenic homozygousMED23variant. This 7.5-year-old boy from consanguineous parents had infantile onset global developmental delay and refractory epilepsy. He was treated with the ketogenic diet at 2.5 years of age and became seizure free on the first day. He had microcephaly and truncal hypotonia. His brain MRI showed delayed myelination and thin corpus callosum. He was enrolled in a whole exome sequencing research study, which identified a novel, homozygous, likely pathogenic (c.1937A>G; p.Gln646Arg) variant inMED23.MED23is a regulator of energy homeostasis and glucose production. Liver-specific Med23-knockout mice showed reduced liver gluconeogenesis and lower blood glucose levels compared to control mice. This is the first patient with documented refractory epilepsy caused by a novel homozygous pathogenic variant inMED23expanding the phenotypic spectrum. Identification of the underlying genetic defect inMED23sheds light on the possible mechanism of complete response to the ketogenic diet in this child. © 2016 Wiley Periodicals, Inc.