Glucose-6-phosphate dehydrogenase (G6PD) deficiency is an X-linked recessive disease that causes acute or chronic hemolytic anemia and potentially leads to severe jaundice in response to oxidative agents. Capicua transcriptional repressor (CIC) is an important gene associated with mental retardation, autosomal dominant 45. Affiliated tissues including skin, brain, bone, and related phenotypes are intellectual disability and seizures. Clinical, biochemical, and whole exome analysis are carried out in a Turkish family. Mutation analysis of G6PD and CIC genes by Sanger sequencing in the whole family was carried out to reveal the effect of these mutations on the patient's clinical outcome. Here, we present the case of epilepsy in an 8-year-old child with a hemizygous variation in G6PD gene and heterozygous mutation in CIC gene, resulting in focal epileptiform activity and hypsarrhythmia in electroencephalography (EEG), seizures, psychomotor retardation, speech impairment, intellectual disability, developmental regression, and learning difficulties. Whole exome sequencing confirmed the diagnosis of X-linked increased susceptibility for hemolytic anemia due to G6PD deficiency and mental retardation type 45 due to CIC variant, which explained the development of epileptic seizures. Considering CIC variant and relevant relation with the severity and course of the disease, G6PD mutations sustained through the family are defined as hereditary. Our findings could represent the importance of variants found in G6PD as well as CIC genes linked to the severity of epilepsy, which was presumed based on the significant changes in protein configuration.

Keywords: CIC mutation; G6PD; Glucose-6-phosphate dehydrogenase deficiency; Mental retardation; Seizure.