Abstract：
OBJECTIVE: We present low-level mosaic trisomy 21 at amniocentesis in a pregnancy associated with cytogenetic discrepancy in various tissues, perinatal progressive decrease of the trisomy 21 cell line and a favorable fetal outcome.
METHODS: A 36-year-old, gravida 2, para 1, woman underwent amniocentesis at 18 weeks of gestation because of advanced maternal age, and the result was 47,XY,+21 [8]/46,XY [26]. Prenatal ultrasound findings were unremarkable. She was referred for genetic counseling, and repeat amniocentesis performed at 23 weeks of gestation revealed the result of 47,XY,+21 [3]/46,XY [21]. The parental karyotypes were normal. At repeat amniocentesis, quantitative fluorescent polymerase chain reaction (QF-PCR) analysis using the DNA extracted from uncultured amniocytes and parental bloods excluded uniparental disomy (UPD) 21, array comparative genomic hybridization (aCGH) analysis on uncultured amniocytes revealed the result of arr 21q11.2q22.3 × 2.4, consistent with 40% mosaicism for trisomy 21, and fluorescence in situ hybridization (FISH) analysis on uncultured amniocytes revealed 67% (67/100 cells) mosaicism for trisomy 21. The woman was advised to continue the pregnancy, and a 1370-g male baby was delivered prematurely at 29 weeks of gestation without phenotypic abnormalities. The karyotypes of umbilical cord and placenta were 47,XY,+21 [13]/46,XY [27] and 47,XY,+21 [40], respectively. QF-PCR determined maternal origin of the extra chromosome 21 of trisomy 21 in the placenta. When follow-up at age 8½ months, the neonate was normal in appearance and development. The peripheral blood had a karyotype of 47,XY,+21 [1]/46,XY [39], and FISH analysis on buccal mucosal cells showed 9.7% (11/113 cells) mosaicism for trisomy 21, compared with 2% (2/100 cells) in the normal control.
CONCLUSIONS: Low-level mosaic trisomy 21 at amniocentesis can be associated with cytogenetic discrepancy in various tissues, perinatal progressive decrease of the trisomy 21 cell line and a favorable fetal outcome.
METHODS: A 36-year-old, gravida 2, para 1, woman underwent amniocentesis at 18 weeks of gestation because of advanced maternal age, and the result was 47,XY,+21 [8]/46,XY [26]. Prenatal ultrasound findings were unremarkable. She was referred for genetic counseling, and repeat amniocentesis performed at 23 weeks of gestation revealed the result of 47,XY,+21 [3]/46,XY [21]. The parental karyotypes were normal. At repeat amniocentesis, quantitative fluorescent polymerase chain reaction (QF-PCR) analysis using the DNA extracted from uncultured amniocytes and parental bloods excluded uniparental disomy (UPD) 21, array comparative genomic hybridization (aCGH) analysis on uncultured amniocytes revealed the result of arr 21q11.2q22.3 × 2.4, consistent with 40% mosaicism for trisomy 21, and fluorescence in situ hybridization (FISH) analysis on uncultured amniocytes revealed 67% (67/100 cells) mosaicism for trisomy 21. The woman was advised to continue the pregnancy, and a 1370-g male baby was delivered prematurely at 29 weeks of gestation without phenotypic abnormalities. The karyotypes of umbilical cord and placenta were 47,XY,+21 [13]/46,XY [27] and 47,XY,+21 [40], respectively. QF-PCR determined maternal origin of the extra chromosome 21 of trisomy 21 in the placenta. When follow-up at age 8½ months, the neonate was normal in appearance and development. The peripheral blood had a karyotype of 47,XY,+21 [1]/46,XY [39], and FISH analysis on buccal mucosal cells showed 9.7% (11/113 cells) mosaicism for trisomy 21, compared with 2% (2/100 cells) in the normal control.
CONCLUSIONS: Low-level mosaic trisomy 21 at amniocentesis can be associated with cytogenetic discrepancy in various tissues, perinatal progressive decrease of the trisomy 21 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，与各种组织的细胞遗传学差异有关。21三体细胞系的围产期进行性减少和有利的胎儿结局。
方法：36岁，Gravida2，para1，妇女在妊娠18周时接受了羊膜穿刺术，结果是47，XY，+21[8]/46,XY[26]。产前超声检查结果无明显变化。她被推荐接受遗传咨询，在妊娠23周时重复羊膜穿刺术显示结果为47，XY，+21[3]/46,XY[21]。亲本核型正常。重复羊膜穿刺术时，使用从未培养的羊膜细胞和亲本血液中提取的DNA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的阵列比较基因组杂交（aCGH）分析显示，ARR21q11.2q22.3×2.4的结果一致对于21三体的镶嵌性和对未培养的羊膜细胞的荧光原位杂交（FISH）分析显示100％建议该妇女继续怀孕，一名1370g男婴在妊娠29周时早产，没有表型异常。脐带和胎盘的核型为47,XY,+21[13]/46,XY[27]和47,XY,+21[40],分别。QF-PCR确定了胎盘中21三体的21号染色体的母体起源。在8½个月的年龄进行随访时，新生儿外观发育正常。外周血核型为47，XY，+21[1]/46,XY[39],颊粘膜细胞的FISH分析显示，三体性21为9.7％（11/113细胞），而正常对照组为2％（2/100细胞）。
结论：羊膜穿刺术中低水平镶嵌三体性21可能与各种组织的细胞遗传学差异有关，21三体细胞系的围产期进行性减少和有利的胎儿结局。
方法：36岁，Gravida2，para1，妇女在妊娠18周时接受了羊膜穿刺术，结果是47，XY，+21[8]/46,XY[26]。产前超声检查结果无明显变化。她被推荐接受遗传咨询，在妊娠23周时重复羊膜穿刺术显示结果为47，XY，+21[3]/46,XY[21]。亲本核型正常。重复羊膜穿刺术时，使用从未培养的羊膜细胞和亲本血液中提取的DNA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的阵列比较基因组杂交（aCGH）分析显示，ARR21q11.2q22.3×2.4的结果一致对于21三体的镶嵌性和对未培养的羊膜细胞的荧光原位杂交（FISH）分析显示100％建议该妇女继续怀孕，一名1370g男婴在妊娠29周时早产，没有表型异常。脐带和胎盘的核型为47,XY,+21[13]/46,XY[27]和47,XY,+21[40],分别。QF-PCR确定了胎盘中21三体的21号染色体的母体起源。在8½个月的年龄进行随访时，新生儿外观发育正常。外周血核型为47，XY，+21[1]/46,XY[39],颊粘膜细胞的FISH分析显示，三体性21为9.7％（11/113细胞），而正常对照组为2％（2/100细胞）。
结论：羊膜穿刺术中低水平镶嵌三体性21可能与各种组织的细胞遗传学差异有关，21三体细胞系的围产期进行性减少和有利的胎儿结局。
