目的:探讨两例发育性癫痫性脑病66型患儿的临床表型及基因变异特点。方法:采集患儿和父母的外周血样，应用全外显子测序的方法对患儿基因进行检测，并采用Sanger测序的方法对变异位点进行验证。结果:两例患儿均为足月儿，主要表现为新生儿期起病的癫痫发作、肌张力低下、全面性发育落后及特殊面容。头颅磁共振提示1例小脑发育不全，1例髓鞘化不良。全外显子测序结果显示两例患儿n PACS2基因均发生了c．625G>A (p.Glu209Lys)杂合变异(NM_001100913.3)，c.625G>A (p.Glu209Lys)变异为已报道过的致病变异。根据《ACMG遗传变异分类标准与指南》，该变异判定为致病性变异(PS2+PM2+PP3)。两例患儿均予丙戊酸钠联合左乙拉西坦治疗后发作控制。至末次随访，两例患儿运动及智力发育情况得到改善。与已报道病例相比，本研究的两例患儿临床症状及体征相对较轻，治疗效果较好。n 结论:PACS2基因c.625G>A (p.Glu209Lys)变异为发育性癫痫性脑病66型的变异热点，基因检测可以为临床诊断和治疗提供依据。n “,”Objective:To explore the clinical phenotype and genetic characteristics of two children with developmental epileptic encephalopathy type 66.Methods:Genomic DNA was extracted from peripheral blood samples of the two children and their parents. Whole-exome sequencing (WES) was carried out and suspected variant was verified by Sanger sequencing.Results:The main manifestations of the two children were neonatal onset seizures, hypotonia, global developmental delay, and facial dysmorphisms. Cranial MRI showed delayed myelination in case 1 and cerebellar dysgenesis in case 2. WES has identified a n de novo pathogenic variant in then PACS2 gene in both patients, namely c. 625G>A (p.Glu209Lys)(NM_001100913.3), which was reported as a pathogenic variant before. This variant was predicted to be pathogenic according to the American College of Medical Genetics and Genomics guideline (PS2+ PM2+ PP3). The seizures were controlled after combination treatment of sodium valproate and levetiracetam in both cases. At last follow-up, the motor and intellectual development of the 2 cases were improved. Compared with the cases reported, the clinical symptoms and signs of our cases were relatively mild, and the treatment effects were fairly good.n Conclusion:The variant of c. 625G>A (p.Glu209Lys) inn PACS2 gene is a hotspot variant of developmental epileptic encephalopathy 66. Gene testing can facilitate the clinical diagnosis and treatment.n