Early-onset epileptic encephalopathy (EOEE) is a kind of epileptic syndrome that appears in neonatal period or early infancy. It has genetic heterogeneity and is characterized by early onset, refractory, multiple seizure types and overall developmental retardation or regression. The clinical data of a child with early-onset epileptic encephalopathy type 27 caused by GRIN2B gene variation were reviewed. The patient was a 12-month-old girl who developed the disease on the second day after birth, presenting with refractory epilepsy, psychomotor retardation, and hypotonia. Cranial magnetic resonance imaging showed bilateral frontal subarachnoid space widening. Long range video electroencephalogram showed multifocal sharp waves and spike waves in each waking and sleeping period, as well as abnormal brain discharges corresponding to the clinical onset, suggesting sharp waves and spike slow waves in the right frontal lobe and central region during sleeping period. Whole exon gene sequencing revealed a novel heterozygous missense variation of c.2635G>A (p. Glu879Lys) (NM_000834) in GRIN2B gene of the proband. The parental and elder brother genotypes were wild-type and the child was considered as early-onset epileptic encephalopathy type 27. No literature was reported on this locus variant. According to the 2015 guidelines of the American College of Medical Genetics and Genomics, it was considered likely pathogenic. Topiramate, ocasepine and rehabilitation function training were used for treatment. During the follow-up, the development of the patient was found to be behind that of normal children of the same age, and there was no epileptic seizure and no abnormal discharge in electroencephalogram. The GRIN2B gene missense variant of (NM_000834):c.2635G>A (p.Glu879Lys) is a possible cause of the proband.
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