Department of Obstetrics and Gynaecology, University of Groningen, University Medical Centre Groningen, Groningen, The Netherlands.
Hum Reprod. 2013 Nov;28(11):3141-5. doi: 10.1093/humrep/det362. Epub 2013 Sep 18.
Preimplantation genetic diagnosis (PGD) is offered to couples carrying a reciprocal translocation in an attempt to increase their chance of phenotypically normal offspring. For the selection of embryos that are balanced for the translocation chromosomes, it is critical to use a combination of DNA probes that can take account of all the segregation patterns of the particular translocation. The frequency of the different segregation types differs depending on the chromosomes involved, the location of the breakpoints and the number of chiasmata and the sex of the carrier. We report on a case of misdiagnosis after PGD-fluorescence in situ hybridization in a female translocation 46,X,t(X;5)(q13;p14) carrier. Transfer of two embryos diagnosed as balanced for the translocation chromosomes resulted in a singleton pregnancy that miscarried at 8 weeks' gestational age. The unbalanced karyotype of the fetus was consistent with 3:1 segregation resulting in tertiary trisomy for the derivative chromosome 5: 47,XX,+der(5)t(X;5)(q13;p14)mat. Based on additional molecular cytogenetic studies of fetal tissue and the initially investigated blastomeres, we concluded that the misdiagnosis was most probably due to a technical error, i.e. a partial hybridization failure or co-localization of the Xq/Yq subtelomere probe signals. No evidence for a normal cell line (mosaicism) was found in the fetus, which could have explained the discrepancy. This case demonstrates the importance of using two diagnostic probes or testing 2 cells to detect translocation products with potentially viable imbalance. X;autosome translocations are a special case due to the added complication of X chromosome inactivation and particular caution is advised when designing a PGD strategy.
not applicable.
胚胎植入前遗传学诊断（PGD）可用于携带相互易位的夫妇，以增加表型正常后代的机会。为了选择平衡易位染色体的胚胎，使用可以考虑特定易位所有分离模式的 DNA 探针组合至关重要。不同分离类型的频率因涉及的染色体、断点位置以及交叉数和携带者的性别而异。我们报告了一例女性易位 46，X，t（X；5）（q13;p14）携带者 PGD-荧光原位杂交后的误诊病例。转移两个诊断为平衡易位染色体的胚胎导致单胎妊娠，妊娠 8 周时流产。胎儿的不平衡核型与 3:1 分离一致，导致衍生染色体 5 的三体型：47，XX，+der（5）t（X；5）（q13;p14）mat。基于对胎儿组织和最初研究的卵裂球的额外分子细胞遗传学研究，我们得出结论，误诊最可能是由于技术错误，即部分杂交失败或 Xq/Yq 端粒探针信号的共定位。在胎儿中未发现正常细胞系（嵌合体），这可以解释差异。该病例表明使用两个诊断探针或检测 2 个细胞以检测具有潜在可行失衡的易位产物的重要性。X；常染色体易位是一个特殊情况，因为 X 染色体失活增加了复杂性，因此在设计 PGD 策略时应特别小心。
不适用。
