表型正常母亲二次孕育21-三体综合征患儿的遗传学分析.

Genetic Analysis of Second Pregnancy with A Child of 21-Trisomy Syndrome in A Phenotypically Normal Mother.

The repeated pregnancies with 21 -trisomy syndrome in a phenotypically normal mother are rare, and the possibility of maternal chromosomal mosaic should be considered. We report a woman with normal phenotype who had a history of early embryo loss for 4 times, two of which the karyotypes were 47,XY,+21. The couple′s karyotypes were normal (counting 20 split phases). Both noninvasive prenatal testing (NIPT) and extended NIPT results refer to a high risk of trisomy 21, and the amniocentesis single nucleotide polymorphism array (SNParray) result was [arr(1-22)×2,(XN×1)], and the fetal amniotic fluid karyotype was 46,XN. The repeated peripheral blood chromosomes test for the couple (counting 50 split phases) was performed, the maternal chromosome karyotype was diagnosed as 47,XX,+21[4]/46,XX[46], with a mosaic ratio of 7%-8%. Maternal fluorescence in situ hybridization (FISH) assay in 100 counted cells showed 7 trisomy 21 cells, suggesting that 7% of the cells were trisomy 21. Fetal amniotic fluid FISH test found no 21-trisomy cell. A healthy baby girl was delivered by cesarean section at 40 +1 weeks of gestation. In this case, maternal karyotype of a mosaic 21 -trisomy cell/normal cell phenotype may contribute to the twice early pregnancy losses with 21-trisomy syndrome. [ABSTRACT FROM AUTHOR]

母亲表型正常而反复孕育21-三体综合征患儿的病例非常罕见, 临床上要考虑母亲染色体嵌 合体的可能. 报告1例表型正常孕妇既往4次妊娠早期胚胎停育, 其中2次胚胎染色体均为47,XY,+21. 夫妻双 方染色体正常 (计数20个分裂象). 此次妊娠无创产前筛查 (noninvasive prenatal testing, NIPT)和扩展型NIPT均 提示21-三体高风险, 羊水穿刺单核苷酸多态性微阵列 (single nucleotide polymorphism array, SNP-array)结果 为[arr(1-22)×2,(XN×1)], 胎儿羊水染色体核型为46,XN. 复查夫妻双方外周血染色体 (计数50个分裂象), 确诊 孕妇染色体为47,XX,+21[4]/46,XX[46], 嵌合比例在7%～8%, 孕妇外周血染色体荧光原位杂交 (fluorescence in situ hybridization, FISH)检测计数100个细胞, 7个21-三体, 即7%的细胞为21-三体. 胎儿羊水FISH检测计数 100个细胞均未见21-三体. 最终于孕40+1 周剖宫产娩一健康女婴. 该病例母亲染色体核型为21-三体嵌合型是 导致连续2次孕育21-三体综合征患儿的原因. [ABSTRACT FROM AUTHOR]