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目的报告1例嵌合型母亲连续2次孕育单纯型21-三体患儿。方法对21-三体患儿、21-三体胎儿和其父母的血标本、父亲精子进行了DNA多态性检测,选择2个SRTR多态性位点,即D21S1412和D21S11,进行荧光定量PCR检测以确定额外21号染色体的起源。对父亲和母亲的外周血染色体和母亲皮肤染色体也进行了分析。结果对2个患儿与双亲的STR结果进行比较,显示2个患儿的额外21号染色体都来自母亲。双亲的STR检测中仅发现有2个微卫星标志物,外周血淋巴细胞染色体也均为正常。但母亲皮肤成纤维细胞检测到21-三体的细胞存在,占4%。结论母亲是21三体细胞/正常细胞的嵌合体,推测母亲生殖细胞中存在21三体细胞与正常细胞的嵌合,这可能是导致连续2次孕育21-三体患儿的原因。
Objective To report a case of chimeric mothers in two consecutive pregnancies of simple 21-trisomy. Methods DNA polymorphism was detected in 21- trisomy, 21- trisomy and their parents’ blood samples, and father’s sperm. Two SRTR polymorphism sites, D21S1412 and D21S11, were selected for fluorescence quantitative PCR Detection to determine the origin of additional chromosome 21. Chromosomes from peripheral blood and mothers’ skin of fathers and mothers were also analyzed. Results The STR results of two children and their parents were compared, showing that both children had extra chromosome 21 from their mother. Only two microsatellite markers were found in the STRs of the parents, and the peripheral blood lymphocyte chromosomes were also normal. However, maternal skin fibroblasts detected the presence of 21-trisomic cells, accounting for 4%. Conclusion The mother is a chimera of trisomy 21 / normal cells. It is speculated that maternal trisomy 21 chimerism is associated with normal cells, which may be the reason of 21 consecutive trisomy 21 births.