Clinical features and ion channel gene mutations analysis in 17 cases of early-onset epileptic encephalopathy

Abstract

Objective To analyze the clinical characteristics and gene mutations of early-onset epileptic encephalopathy(EOEE) caused by ion channel gene mutation, to identify the etiology, to guide the treatment and to provide the basis for genetic counseling. Methods The clinical data from 17 children with EOEE caused by ion channel gene mutation and the peripheral blood of the children and their parents were collected from June 2014 to May 2018 at the Department of Neurology, Tianjin Children′s Hospital.Epilepsy gene sequencing was performed by using disease gene targeting second generation sequencing technology.The mutation of pathogenic ion channel gene was found.The confirmed mutations were verified by Sanger sequencing and the source of the mutation was identified. Results Among 17 case with EOEE, 3 cases had genetic mutation, and 14 cases had denovo mutations.Dravet syndrome was found in 8 cases (47.1%), there were SCN1A gene missense mutation in 5 cases, SCN1A gene nonsense mutation in 3 cases, KCNQ2 gene missense mutation in 1 case (5.9%) and non-specific epileptic encephalopathy in 8 cases (47.1%). SCN2A gene missense mutation, SCN4A gene missense mutation, SCN8A gene missense mutation, KCNQ2 gene missense mutation and KCNH gene missense mutation were found in suspected pathogenic mutations.There were 1 missense mutation out of 5 genes, 1 missense mutation of CACNA1A gene, 1 missense mutation of GRIN2A gene and 1 missense mutation of GRIN3A gene.Seventeen patients were treated with 2 or more antiepileptic drugs, 4 with ketogenic diet and 1 with vitamin B6 supplementation.During 11 to 96 months of follow-up, seizures were completely controlled in 3 cases (17.6%), decreased in 7 cases (41.2%) by more than 50%, and decreased in 7 cases (41.2%) by less than 50%. Conclusions The clinical phenotypes for children with unexplained EOEE are varied, and gene mutations of ion cha-nnel are most common.Some gene sites are denovo mutations which have not been reported such as missense mutation for 3 case SCN1A gene, 1 case SCN2A gene, 1 case CACNA1A gene, 1 case KCNH5 gene, and nonsense mutation for 2 case SCN1A gene, which have enriched the mutation spectrum of EOEE. Key words: Early-onset epileptic encephalopathy; Ion channel; Etiology; Gene mutation