Dravet综合征少见致病基因突变及临床表型分析

摘要

目的 研究Dravet综合征(DS)少见致病基因突变,并对携带少见致病基因突变的患儿进行基因型-表型分析.方法 收集2005年2月至2016年8月在北京大学第一医院儿科就诊的DS患儿,采用Sanger测序及多重连接依赖的探针扩增(MLPA)方法筛查SCN1A及PCDH19基因突变,对SCN1A及PCDH19基因突变阴性的患儿进行癫痫基因靶向捕获二代测序;分析携带少见致病基因突变患儿的临床表型特点.结果 在670例DS患儿中,SCN1A突变阳性者556例(83.0％),PCDH19突变阳性者6例,余108例SCN1A及PCDH19突变筛查阴性者送检癫痫基因靶向捕获二代测序,发现12例携带其他致病基因突变,其中GABRA1杂合突变3例,GABRG2杂合突变2例,GABRB2杂合突变2例,SCN2A杂合突变1例,TBC1D24复合杂合突变2例,ALDH7A1复合杂合突变2例.6例PCDH19杂合突变者发作均有丛集性,仅1例病程中曾出现癫痫持续状态;2例GABRB2杂合突变者发作控制相对好;2例TBC1 D24复合杂合突变者均出现多次肌阵挛持续状态;2例ALDH7A1复合杂合突变者加用维生素B6发作控制.未发现GABRG2、SCN2A和GABRA1基因突变导致的DS表型有特异性.结论 中国DS患儿可出现的少见致病基因突变包括PCDH19、GABRG2、SCN2A、GABRA1、GABRB2、TBC1D24和ALDH7A1基因.GABRB2和TBC1D24基因突变的发现扩展了DS的致病基因谱.PCDH19突变者丛集性发作突出,癫痫持续状态少见;GABRB2突变者发作相对容易控制;TBC11D24复合杂合突变者肌阵挛发作持续状态突出.%Objective To identify the rare causative genes of Dravet syndrome (DS) in patients who do not have SCN1A mutation and to analyze genotypes and phenotypes of DS patients with different rare causative genes.Methods DS patients were collected from the Pediatric Department of Peking University First Hospital from February 2005 to August 2016.SCN1A and PCDH19 gene mutations were screened by Sanger sequencing and multiple ligation-dependant probe amplification (MLPA).Next generation sequencing (NGS) for epilepsy-related gene-panel was applied to SCN1A and PCDH19 mutation-negative patients.The phenotypes of DS patients with different rare causative genes were analyzed.Results Six hundred and seventy patients with DS were collected and 556 patients (83.0％)carried SCN1A mutations and 6 patients with PCDH19 mutations.Epilepsy-related gene-panel was applied to remain 108 patients without SCN1A or PCDH19 mutation,and among them 12 patients were detected with 6 rare causative genes,with heterozygous mutations in GABRA1 mutations in 3,GABRG2 in 2 cases,GABRB2 mutations in 2 cases and SCN2A mutation in 1 case,complex heterozygous mutations in TBC1D24 in 2 cases and ALDH7A1 in 2 cases.The clinical phenotypes of 6 patients with PCDH19 mutations were featured by clustering of repeated seizures with short periods of times,only 1 case had an episode of status epilepticus.Patients with GABRB2 mutations had a relatively better outcome of seizure control.Many episodes of myoclonic status were emerging as hallmark features in patients with TBC1D24 mutations.Vitamin B had a dramatic therapeutic effect in patients with ALDH7A1 mutations.The clinical phenotypes of DS patients with GABRG2,SCN2A and GABRA1 had no obvious specificity.Conclusions The rare causative genes in DS patients include PCDH19,GABRG2,SCN2A,GABRA1,GABRB2,TBC1D24 and ALDH7A1.The finding of causative genes GABRB2 and TBC1D24 may enrich the gene spectrum of DS.Patients with PCDH19 mutations are featured by clustering of repeated seizures with short periods of time and rare status epilepticus.Patients with GABRB2 mutations have a relatively better outcome of seizure control.Many episodes of myoclonic status are emerging as hallmark features in patients with TBC1D24 mutations.