Study of a fetus with confined placental mosaicism for trisomy 2 in conjunct with fetal uniparental disomy and a literature review
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目的 对1例2号染色体三体(T2)限制性胎盘嵌合体(CPM)合并胎儿单亲二体(UPD)的妊娠进行遗传学分析，结合其临床特征，探讨T2 CPM的临床意义。 方法 对1例无创产前检测(NIPT)提示胎儿2号染色体高风险的孕妇进行羊水染色体核型分析，同时进行单核苷酸多态性微阵列(SNP array)和家系全外显子组测序(trio-WES)检测。通过超声波检查密切监测胎儿的生长发育情况。产后对胎盘进行多点取样和基因组拷贝数变异测序(CNV-seq)，以明确其遗传学病因。 结果 胎儿染色体核型未见异常，SNP array发现其2号染色体存在多个杂合性缺失片段，trio-WES检测确认为母源性2号染色体UPD。超声提示胎儿宫内发育迟缓，羊水过少，于孕23+4周宫内死亡。引产儿病理学检查未发现器官异常。胎盘经CNV-seq检测确认为完全性T2。 结论 T2 CPM可造成NIPT假阳性，同时可能合并胎儿UPD，出现宫内发育迟缓、羊水过少、胎死宫内等严重的并发症。 Objective To carry out genetic analysis for a fetus with confined placental mosaicism (CPM) for trisomy 2 (T2) in conjunct with fetal uniparental disomy (UPD). Methods Amniocentesis and chromosomal karyotyping was carried out for a pregnant woman with a high risk for chromosome 2 anomalies indicated by non-invasive prenatal testing (NIPT). Single nucleotide polymorphism array (SNP array) and trio-whole exome sequencing (Trio-WES) were carried out. Ultrasonography was used to closely monitor the fetal growth. Multifocal sampling of the placenta was performed after delivery for copy number variation sequencing (CNV-seq). Results The fetus was found to have a normal chromosomal karyotype. SNP-array has revealed multiple regions with loss of heterozygosity (LOH) on chromosome 2. Trio-WES confirmed the presence of maternal UPD for chromosome 2. Ultrasonography has revealed intrauterine growth restriction and oligohydramnios. Intrauterine fetal demise had occurred at 23+ 4 weeks of gestation. Pathological examination had failed to find salient visceral abnormality. The placenta was proved to contain complete T2 by CNV-seq. Conclusion T2 CPM can cause false positive result for NIPT and may be complicated with fetal UPD, leading to adverse obstetric outcomes such as intrauterine growth restriction, oligohydramnios and intrauterine fetal demise.
Objective To carry out genetic analysis for a fetus with confined placental mosaicism (CPM) for trisomy 2 (T2) in conjunct with fetal uniparental disomy (UPD). Methods Amniocentesis and chromosomal karyotyping was carried out for a pregnant woman with a high risk for chromosome 2 anomalies indicated by non-invasive prenatal testing (NIPT). Single nucleotide polymorphism array (SNP array) and trio-whole exome sequencing (Trio-WES) were carried out. Ultrasonography was used to closely monitor the fetal growth. Multifocal sampling of the placenta was performed after delivery for copy number variation sequencing (CNV-seq). Results The fetus was found to have a normal chromosomal karyotype. SNP-array has revealed multiple regions with loss of heterozygosity (LOH) on chromosome 2. Trio-WES confirmed the presence of maternal UPD for chromosome 2. Ultrasonography has revealed intrauterine growth restriction and oligohydramnios. Intrauterine fetal demise had occurred at 23+ 4 weeks of gestation. Pathological examination had failed to find salient visceral abnormality. The placenta was proved to contain complete T2 by CNV-seq. Conclusion T2 CPM can cause false positive result for NIPT and may be complicated with fetal UPD, leading to adverse obstetric outcomes such as intrauterine growth restriction, oligohydramnios and intrauterine fetal demise.
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