Abstract：
OBJECTIVE: We present low-level mosaic trisomy 21 at amniocentesis in a pregnancy with a favorable fetal outcome.
METHODS: A 34-year-old, primigravid woman underwent amniocentesis at 17 weeks of gestation because of advanced maternal age. Amniocentesis revealed a karyotype of 47,XY,+21 [7]/46,XY [33]. At 23 weeks of gestation, repeat amniocentesis revealed a karyotype of 47,XY,+21 [4]/46,XY [22], and cord blood sampling revealed the karyotype of 47,XY,+21 [5]/46,XY [35]. The parental karyotypes were normal. Quantitative fluorescent polymerase chain reaction (QF-PCR) analysis on uncultured amniocytes and parental bloods excluded UPD 21, array comparative genomic hybridization (aCGH) analysis on uncultured amniocytes revealed the result of arr 21q11.2q22.3 × 2.3, consistent with 30% mosaicism for trisomy 21. Interphase fluorescence in situ hybridization (FISH) analysis on uncultured amniocytes revealed 43.8% (35/80 cells) mosaicism for trisomy 21. The woman was advised to continue the pregnancy, and a phenotypically normal 3,340-g male baby was delivered at 39 weeks of gestation. The cord blood had a karyotypes of 46,XY (40/40 cells). QF-PCR on placenta showed mosaic trisomy 21. When follow-up at age three months, the neonate was normal in phenotype and development. FISH analysis on buccal mucosal cells showed 9% (10/101 cells) mosaicism for trisomy 21, compared with 0% (0/100 cells) in the normal control.
CONCLUSIONS: Low-level mosaic trisomy 21 at amniocentesis can be associated with cytogenetic discrepancy between cultured amniocytes and uncultured amniocytes, perinatal progressive decrease of the aneuploid cell line and a favorable fetal outcome.
METHODS: A 34-year-old, primigravid woman underwent amniocentesis at 17 weeks of gestation because of advanced maternal age. Amniocentesis revealed a karyotype of 47,XY,+21 [7]/46,XY [33]. At 23 weeks of gestation, repeat amniocentesis revealed a karyotype of 47,XY,+21 [4]/46,XY [22], and cord blood sampling revealed the karyotype of 47,XY,+21 [5]/46,XY [35]. The parental karyotypes were normal. Quantitative fluorescent polymerase chain reaction (QF-PCR) analysis on uncultured amniocytes and parental bloods excluded UPD 21, array comparative genomic hybridization (aCGH) analysis on uncultured amniocytes revealed the result of arr 21q11.2q22.3 × 2.3, consistent with 30% mosaicism for trisomy 21. Interphase fluorescence in situ hybridization (FISH) analysis on uncultured amniocytes revealed 43.8% (35/80 cells) mosaicism for trisomy 21. The woman was advised to continue the pregnancy, and a phenotypically normal 3,340-g male baby was delivered at 39 weeks of gestation. The cord blood had a karyotypes of 46,XY (40/40 cells). QF-PCR on placenta showed mosaic trisomy 21. When follow-up at age three months, the neonate was normal in phenotype and development. FISH analysis on buccal mucosal cells showed 9% (10/101 cells) mosaicism for trisomy 21, compared with 0% (0/100 cells) in the normal control.
CONCLUSIONS: Low-level mosaic trisomy 21 at amniocentesis can be associated with cytogenetic discrepancy between cultured amniocytes and uncultured amniocytes, perinatal progressive decrease of the aneuploid cell line and a favorable fetal outcome.
摘要：
目的：我们在妊娠羊膜腔穿刺术中呈现低水平镶嵌三体21，胎儿结局良好。
方法：34岁，由于母亲年龄高，初产妇在妊娠17周时接受了羊膜穿刺术。羊膜穿刺术显示核型为47，XY，+21[7]/46,XY[33]。妊娠23周时，重复羊膜穿刺术显示核型为47，XY，+21[4]/46,XY[22],脐带血采样显示核型为47，XY，+21[5]/46,XY[35]。亲本核型正常。对未培养的羊膜细胞和排除UPD21的亲本血液进行定量荧光聚合酶链反应（QF-PCR）分析，对未培养的羊膜细胞进行阵列比较基因组杂交（aCGH）分析显示ARR21q11.2q22.3×2.3的结果，与三体性21的镶嵌性30％一致。对未培养的羊膜细胞的相间荧光原位杂交（FISH）分析显示，21三体的镶嵌性为43.8％（35/80细胞）。建议该妇女继续怀孕，一名表型正常的3,340g男婴在妊娠39周时分娩。脐带血的核型为46，XY（40/40细胞）。胎盘上的QF-PCR显示马赛克三体21。在三个月的年龄进行随访时，新生儿表型和发育正常。口腔粘膜细胞的FISH分析显示，三体性21的镶嵌性达到9％（10/101个细胞），而正常对照为0％（0/100个细胞）。
结论：羊膜穿刺术中低水平镶嵌三体性21可能与培养的羊膜细胞和未培养的羊膜细胞之间的细胞遗传学差异有关，围产期非整倍体细胞系的进行性减少和有利的胎儿结局。
方法：34岁，由于母亲年龄高，初产妇在妊娠17周时接受了羊膜穿刺术。羊膜穿刺术显示核型为47，XY，+21[7]/46,XY[33]。妊娠23周时，重复羊膜穿刺术显示核型为47，XY，+21[4]/46,XY[22],脐带血采样显示核型为47，XY，+21[5]/46,XY[35]。亲本核型正常。对未培养的羊膜细胞和排除UPD21的亲本血液进行定量荧光聚合酶链反应（QF-PCR）分析，对未培养的羊膜细胞进行阵列比较基因组杂交（aCGH）分析显示ARR21q11.2q22.3×2.3的结果，与三体性21的镶嵌性30％一致。对未培养的羊膜细胞的相间荧光原位杂交（FISH）分析显示，21三体的镶嵌性为43.8％（35/80细胞）。建议该妇女继续怀孕，一名表型正常的3,340g男婴在妊娠39周时分娩。脐带血的核型为46，XY（40/40细胞）。胎盘上的QF-PCR显示马赛克三体21。在三个月的年龄进行随访时，新生儿表型和发育正常。口腔粘膜细胞的FISH分析显示，三体性21的镶嵌性达到9％（10/101个细胞），而正常对照为0％（0/100个细胞）。
结论：羊膜穿刺术中低水平镶嵌三体性21可能与培养的羊膜细胞和未培养的羊膜细胞之间的细胞遗传学差异有关，围产期非整倍体细胞系的进行性减少和有利的胎儿结局。
