PDF(Pubmed)
Abstract：
We present a case of a fetus acquiring two different balanced translocations from each parent and subsequent uniparental isodisomy from postzygotic loss of a paternal chromosome. Balanced chromosomal translocations occur in 0.14% of the population and increase the risk of other genetic abnormalities, such as uniparental disomy (UPD) and mosaicism. Preimplantation genetic testing (PGT) can identify some genetic abnormalities. Translocations t(6;21) and t(5;15) have been reported individually but never together in a viable fetus. A non-consanguineous couple who were known carriers of two different balanced translocations conceived via classic in vitro fertilization (IVF). They had a normal PGT completed. Chorionic villus sampling (CVS) revealed that the fetus had received t(6;21) from the mother and t(5;15) from the father. The probability of the fetus acquiring both translocations was 2.8%. CVS also revealed UPD of chromosome 14. Amniocentesis was performed, which was consistent with the CVS in detecting the balanced translocations but provided more information about the UPD, determining that it was a mosaic maternal uniparental isodisomy of chromosome 14 (UPD(14)mat). The couple underwent genetic counseling to discuss the above findings and ultimately decided on dilation and evacuation at 17 weeks of gestation. The likelihood of conception of this fetus and survival past the first trimester is extremely rare. These specific chromosomal translocations and (UPD(14)mat) have never been reported before. This case emphasizes the concomitant nature of imprinted genes, resulting in multiple genetically unique alterations. This report also highlights the limitations of PGT, CVS, and amniocentesis in being reproducibly consistent, which is important to discuss prior to IVF conception.
摘要：
我们介绍了一个案例，即胎儿从每个父母获得两个不同的平衡易位，然后从父系染色体的合子后丢失获得单亲等异体性。平衡的染色体易位发生在0.14%的人群中，并增加其他遗传异常的风险，例如单亲二分法(UPD)和镶嵌主义。植入前基因检测（PGT）可以识别一些遗传异常。已经单独报道了t(6;21)和t(5;15)易位,但从未在存活胎儿中一起。一对非近亲夫妇，他们是通过经典体外受精（IVF）构思的两种不同平衡易位的已知携带者。他们完成了正常的PGT。绒毛膜绒毛取样（CVS）显示，胎儿从母亲那里接受了t（6;21），从父亲那里接受了t（5;15）。胎儿获得两种易位的概率为2.8％。CVS还揭示了14号染色体的UPD。进行了羊膜穿刺术,这与CVS在检测平衡易位方面一致，但提供了更多关于UPD的信息，确定这是14号染色体的镶嵌母体单亲等异体性（UPD（14）mat）。这对夫妇接受了遗传咨询，以讨论上述发现，并最终决定在妊娠17周时进行扩张和疏散。受孕这个胎儿和存活超过前三个月的可能性非常罕见。以前从未报道过这些特定的染色体易位和（UPD（14）mat）。这个案例强调了印记基因的伴随性质，导致多种遗传上独特的改变。本报告还强调了PGT的局限性，CVS,羊膜穿刺术是可重复的，在试管婴儿概念之前讨论这一点很重要。
