摘要目的:通过对两对患1型神经纤维瘤（neurofibromatosis type 1，NF1）的同卵双胞胎进行全基因组测序分析对比儿童先天性骨假关节（congenital pseudarthrosis，CP）表型和非CP表型患儿的分子特征，鉴定CP患儿的致病变异，并对相关表型和1型神经纤维瘤致病基因 NF1变异进行特征描述。 方法:根据胫骨假关节诊断标准和NF1临床诊断标准，纳入两对均患有NF1的同卵双胞胎，均为女性，且每对双胞胎中均仅1人有CP表型。对两对同卵双胞胎的外周血提取DNA进行全基因组测序，运用生物信息学方法分析单核苷酸变异（single nucleotide variant，SNV）、短插入缺失变异（short insertion deletion variants，InDel）、拷贝数变异（copy number variant，CNV）和结构变异（structural variant，SV），鉴定出涉及 NF1基因的致病变异及CP患者特有的胚系致病变异；对鉴定出的致病变异在双胞胎及父母中进行一代测序验证。 结果:两对NF1型同卵双胞胎中均鉴定到 NF1基因的致病胚系变异，分别为：c.3047_3048del（p.Cys1016SerfsTer4）和c.4267A>G（p.Lys1423Glu）杂合变异；经过家系4人的一代测序验证，表明均为新发变异。除 NF1基因外，在CP患儿特有而未患CP的同胞姐妹没有的变异中，未鉴定到其他致病或可能致病的SNV/InDel、结构变异或CNV变异。进一步比较两对双胞胎中CP患儿特有的评级为意义不明的低频有害错义变异和功能缺失型SNV和InDels变异，发现这些变异共同影响的基因有1 802个，无共同基因存在编码区的变异；评级为意义不明的结构变异或CNV变异所在的基因无交集，即无共同变异基因。 结论:全基因组测序分析揭示两对患有NF1同卵双胞胎均鉴定到了1型神经纤维瘤致病基因 NF1的致病变异，未鉴定到双胞胎中CP患者特有的其他致病变异，且两个CP患者中未检测到其他的共同基因包含可能致病的变异。

abstractsObjective:To compare the genotypes and phenotypes between the monozygotic twins via whole genome sequencing to further clarify the autosomal dominant inherited neurofibromatosis type 1 (NF1) variants related to congenital pseudarthrosis (CP).Methods:According to the diagnostic criteria of congenital tibial pseudarthrosis and the clinical diagnostic criteria of NF1, two pairs of monozygotic twins with NF1 were included. Both were female and only one of each pair had congenital pseudarthrosis. The other did not have congenital pseudarthrosis. Whole genome sequencing was performed using the peripheral blood of the two pairs of monozygotic twins. Customized bioinformatics analysis was then performed to identify single nucleotide variants (SNVs), short insertion deletion variants (InDel), copy number variants (CNVs), and structural variants (SVs). Classified the variants according to the American College of Medical Genetics and Genomics (ACMG) and ClinGen criteria. The germline variants within the monozygotic twins were compared to identify the CP patients' unique variants. The shared pathogenic or likely pathogenic germline variants between the unique variants in the CP patients from the twins were also analyzed. Further, the identified disease-causing variants were validated by Sanger sequencing in the family of the twins and their parents. Finally, the genotypes and phenotypes regarding the pathogenic variants of the NF1 gene among the twins were characterized. Results:Both the two monozygotic twins were identified pathogenic variants in the NF1 gene. One with c.3047_3048del (p.Cys1016SerfsTer4), and the other with c.4267A>G (p.Lys1423Glu). By Sanger sequencing validation in family quads, the two CP patients and their siblings harbored de novo heterozygous variants of the NF1 gene. In addition to the NF1 gene, no other genes were identified pathogenic or likely pathogenic variants uniquely in the CP patients compared with their twin sisters, as well as SVs and CNVs. In addition, by analyzing the rare and damaging variants in the two CP patients from the two twins, they had no overlapping genes against the SNVs, InDels, SVs, or CNVs. Conclusion:Whole genome sequencing revealed that both the two monozygotic twins with NF1 were detected pathogenic variants of gene NF1. No other pathogenic variants specific to the CP patients among the twins were identified. The two CP patients shared no other common genes from the detected likely pathogenic variants.