早期癫性脑病临床表型和基因突变特征及二代基因测序在病因诊断中的应用

Clinical phenotype, gene mutation and application of targeted next generation sequencing in patients with early-onset epileptic encephalopathy

目的总结早期癫性脑病患儿临床表型和基因突变特征,探讨二代基因测序在病因诊断中的应用。方法收集68例早期癫性脑病患儿临床资料,采集患儿及其父母外周静脉血,采用二代基因测序筛选可疑致病性突变,并经Sanger测序验证基因突变来源。结果 68例早期癫性脑病患儿中18例(26.47%)检测出癫相关致病基因,明确诊断为吡哆醇依赖性癫1例,系ALDH7A1基因突变所致;硫胺素代谢紊乱综合征2型1例,系SLC19A3基因突变所致。13例病因明确的癫综合征中Dravet综合征6例,5例系SCN1A基因错义突变所致,1例系SCN1A基因无义突变所致;婴儿痉挛症4例,1例系TSC1基因无义突变所致,但无法确定该基因的致病性,3例未见可疑致病性突变;早期婴儿型癫性脑病(亦称为大田原综合征)2例,1例系STXBP1基因错义突变所致,1例未见可疑致病性突变;婴儿严重局灶性游走性癫1例,未见可疑致病性突变。53例非特异性癫性脑病中9例发现可疑致病性突变,1例为SCN8A基因错义突变、1例KCNQ2基因错义突变、1例KCNH5基因错义突变、1例CACNA1A基因错义突变、2例CDKL5基因无义突变、1例CDKL5基因框移突变、1例PCDH19基因无义突变、1例GRIN2A基因错义突变。均予2种及以上抗癫药物治疗,1例明确诊断为吡哆醇依赖性癫后,予维生素B620 mg(/kg·d);1例明确诊断为硫胺素代谢紊乱综合征2型后,予维生素B125 mg(/kg·d)和生物素2 mg(/kg·d)。平均随访6个月至8年,15例(22.06%)癫发作控制良好,21例(30.88%)癫发作部分控制,32例(47.06%)癫发作未控制。结论早期癫性脑病临床表型多样,经基因检测明确诊断吡哆醇依赖性癫和硫胺素代谢紊乱综合征2型各1例,对于可治疗的遗传性疾病针对病因治疗,癫发作控制良好。3例SCN1A基因错义突变、1例STXBP1基因错义突变、1例KCNH5基因错义突变、1例CACNA1A基因错义突变、1例CDKL5基因框移突变、1例PCDH19基因无义突变为新发突变,丰富了早期癫性脑病的临床表型和基因谱。

Objective To study the clinical features and gene mutations of early-onset epileptic encephalopathy （EOEE） and to explore the application in pathogenic diagnosis of EOEE by next generation sequencing. Methods The clinical data of 68 cases diagnosed with unexplained EOEE between June 2014 and December 2017 were obtained and analyzed. Specimens were collected from the selected children and their parents. Next generation sequencing was used to detect epilepsy-related genes, and Sanger sequencing was performed to verify the results and confirm the source of parents, further to identify suspected pathogenic mutations of EOEE. Results Among 68 cases with EOEE, 18 cases （26.47%） were detected with epilepsy-related genes. One was diagnosed as pyridoxine dependent epilepsy （PDE）, which was caused by ALDH7A1 mutation. One was diagnosed as thiamine metabolism dysfunction syndrome 2 （THMD2）, which was caused by SLC19A3 mutation. Among 13 cases of epilepsy syndrome, 6 cases were diagnosed as Dravet＇s syndrome （DS）, 5 caused by SCNIA missense mutation and one by SCNIA nonsense mutation; 4 cases were diagnosed as infantile spasm （IS）, one caused by TSC1 nonsense mutation but the pathogenicity can not be identified while pathogenic mutations were not detected in other 3 cases; 2 cases were diagnosed as Ohtahara＇s syndrome （OS）, one caused by STXBP1 missense mutation and pathogenic mutation was not found in the other; one case of malignant migrating partial seizures in infancy （MMPEI） was not found the pathogenic mutations. Among 53 cases with non-specific EOEE, suspected pathogenic mutations were detected in 9 cases： one case of SCN8A missense mutation, one case of KCNQ2 missense mutation, one case of KCNH5 missense mutation, one case of CACNA1A missense mutation, 2 cases of CDKL5 nonsense mutation, one case of CDKL5 frame- shift mutation, one case of PCDH19 nonsense mutation and one case of GRIN2A missense mutation. All cases were treated by 2 and more antiepileptic drugs （AEDs）, one case of PDE was given vitamin B6 20 mg/（kg, d）, and one case of THMD2 was given vitamin B~ 25 mg/（kg＂ d） and biotin 2 mg/（kg, d）. After followed by 6 months to 8 years, 15 cases （22.06%） were seizure free, 21 cases （30.88%） were part of control and 32 cases （47.06%） were out of control. Conclusions The clinical phenotypes of children with unexplained EOEE are varied. One case was diagnosed as PDE and one as THMD2 after gene sequencing. After treated by etiological treatment, patients with remediable genetic disease were seizure free. Some gene sites were denovo mutations which have not been reported such as missense mutation for SCNIA, STXBP1, KCNH5, CACNA1A, frame-shift mutation for CDKL5, and nonsense mutation for PCDH19, which enriched the mutation spectrum of EOEE.