罕见完全性易位型18-三体的产前遗传学诊断及溯源分析

Prenatal Genetic Diagnosis and Origin Analysis of Rare Complete Translocation Trisomy 18

【目的】探讨无创产前检测(NIPT)提示18-三体高风险胎儿的罕见异常核型起源及对生育的影响。【方法】产前诊断一例罕见完全性易位型18-三体病例,结合细胞及分子遗传学分析对胎儿染色体异常进行溯源。以“易位型18-三体”、“18-三体易位型”(包括中、英文)为检索词,对PubMed、CNKI、SinoMed文献服务系统、万方数据知识服务平台、维普中文科技期刊数据库及中华医学期刊全文数据库进行检索,收集并分析检索到的病例资料。【结果】胎儿SNP array提示18-三体,经父母G-显带核型分析验证,孕妇外周血染色体核型为46,XX,t(9;18)(q31.2;q23),胎儿最终确认核型为47,XN,t(9;18)(q31.2;q23)mat,+18,为罕见的完全性易位型18-三体;与父母SNP array溯源分析显示胎儿有2份完整18号染色体遗传物质来自染色体平衡易位的母亲。文献检索发现国外报道2例完全性易位型18-三体患儿,均有18-三体表型且都来源于亲本18号染色体与其他染色体的平衡易位。【结论】NIPT能有效提前预警或预诊18-三体;SNP array技术不仅能提高染色体异常的检出率,还可以对异常染色体进行溯源;胎儿细胞染色体核型分析仍是产前诊断染色体异常的金标准。

【Objective】To discuss the origin of rare abnormal karyotypes of fetuses with high risk of trisomy 18 re⁃vealed by non-invasive prenatal testing(NIPT)and its impact on fertility.【Methods】The cytogenetic and molecular genet⁃ic analyses were performed on the abnormal chromosomes of a prenatally diagnosed fetus with rare complete translocation trisomy 18.Using the keywords“translocation trisomy 18”or“trisomy 18 translocation”in both Chinese and English,we searched PubMed,CNKI,SinoMed,WanFang Data,CQ VIP and the Chinese Medicine database.The relevant case se⁃ries were retrieved and critically appraised.【Results】G-banded karyotype analysis showed that the maternal karyotype was 46,XX,t(9;18)(q31.2;q23)and the fetal karyotype was 47,XN,t(9;18)(q31.2;q23)mat,+18,which was a rare complete translocation type of trisomy 18.The SNP array revealed the fetus had increased copy number of chromosome 18 and two complete chromosome 18 inherited from the mother with balanced chromosomal translocation.Literature search found two children with complete translocation trisomy 18 reported abroad.Both of them had trisomy 18 phenotype and orig⁃inated from the balanced translocation between parental chromosome 18 and other chromosomes.【Conclusion】NIPT gives an effective advance warning of trisomy 18.SNP array not only improves the detection rate of chromosomal abnormalities,but also helps identify the origin.The karyotype is still the gold standard for prenatal diagnosis.