Abstract：
OBJECTIVE: We present prenatal diagnosis of pseudomosaicism for trisomy 20 at amniocentesis with a negative non-invasive prenatal testing (NIPT) result in a pregnancy with a favorable outcome.
METHODS: A 33-year-old, primigravid woman underwent amniocentesis at 17 weeks of gestation, which revealed a karyotype of 47,XX,+20[8]/46,XX[31]. Simultaneous array comparative genomic hybridization (aCGH) analysis on the DNA extracted from uncultured amniocytes revealed the result of arr (1-22,X) × 2, consistent with no genomic imbalance. She was referred to the hospital for repeat amniocentesis at 23 weeks of gestation. At repeat amniocentesis, cultured amniocytes had a karyotype of 47,XX,+20[2]/46,XX[33]. The parental karyotypes were normal. Simultaneous aCGH analysis on the DNA extracted from uncultured amniocytes using SurePrint G3 Unrestricted CGH ISCA v2, 8 × 60 K (Agilent Technologies, Santa Clara, CA, USA) revealed no genomic imbalance, or arr (1-22,X) × 2, Y × 0. Interphase fluorescence in situ hybridization (FISH) analysis using the bacterial artificial chromosome (BAC) probes of RP11-266K16 [20q13.33; fluorescein isothiocyanate (FITC), spectrum green] and RP11-348I14 (20q11.1-q11.21; Texas Red, spectrum red) detected trisomy 20 signals in 4/104 uncultured amniocytes (3.8%), compared with 0/100 in the normal control. Polymorphic DNA marker analysis using the DNA extracted from uncultured amniocytes and parental bloods excluded uniparental disomy 20. NIPT analysis on maternal blood revealed a negative result without gene dosage increase in chromosome 20. The pregnancy was carried to term, and a healthy 2830-g female baby was delivered with no phenotypic abnormality. Both cord blood and placenta had a karyotype of 46,XX.
CONCLUSIONS: NIPT is useful for rapid differential diagnosis of pseudomosaicism from true mosaicism in case of mosaic trisomy 20 at amniocentesis.
METHODS: A 33-year-old, primigravid woman underwent amniocentesis at 17 weeks of gestation, which revealed a karyotype of 47,XX,+20[8]/46,XX[31]. Simultaneous array comparative genomic hybridization (aCGH) analysis on the DNA extracted from uncultured amniocytes revealed the result of arr (1-22,X) × 2, consistent with no genomic imbalance. She was referred to the hospital for repeat amniocentesis at 23 weeks of gestation. At repeat amniocentesis, cultured amniocytes had a karyotype of 47,XX,+20[2]/46,XX[33]. The parental karyotypes were normal. Simultaneous aCGH analysis on the DNA extracted from uncultured amniocytes using SurePrint G3 Unrestricted CGH ISCA v2, 8 × 60 K (Agilent Technologies, Santa Clara, CA, USA) revealed no genomic imbalance, or arr (1-22,X) × 2, Y × 0. Interphase fluorescence in situ hybridization (FISH) analysis using the bacterial artificial chromosome (BAC) probes of RP11-266K16 [20q13.33; fluorescein isothiocyanate (FITC), spectrum green] and RP11-348I14 (20q11.1-q11.21; Texas Red, spectrum red) detected trisomy 20 signals in 4/104 uncultured amniocytes (3.8%), compared with 0/100 in the normal control. Polymorphic DNA marker analysis using the DNA extracted from uncultured amniocytes and parental bloods excluded uniparental disomy 20. NIPT analysis on maternal blood revealed a negative result without gene dosage increase in chromosome 20. The pregnancy was carried to term, and a healthy 2830-g female baby was delivered with no phenotypic abnormality. Both cord blood and placenta had a karyotype of 46,XX.
CONCLUSIONS: NIPT is useful for rapid differential diagnosis of pseudomosaicism from true mosaicism in case of mosaic trisomy 20 at amniocentesis.
摘要：
目的：我们提出产前诊断羊膜穿刺术中20三体性假性畸形，非侵入性产前检测（NIPT）阴性导致妊娠结局良好。
方法：33岁，初产妇在妊娠17周时接受了羊膜穿刺术，显示核型为47，XX，+20[8]/46,XX[31]。对从未培养的羊膜细胞中提取的DNA进行的同时阵列比较基因组杂交（aCGH）分析显示了arr（1-22，X）×2的结果，与基因组不平衡一致。在妊娠23周时，她被转诊到医院进行再次羊膜穿刺术。重复羊膜穿刺术时，培养的羊膜细胞核型为47，XX，+20[2]/46,XX[33]。亲本核型正常。使用SurePrintG3无限制CGHISCAv2，8×60K（AgilentTechnologies，圣克拉拉,CA,美国)没有发现基因组失衡，或ARR(1-22,X)×2,Y×0。使用RP11-266K16[20q13.33;异硫氰酸荧光素（FITC）的细菌人工染色体（BAC）探针进行间期荧光原位杂交（FISH）分析，光谱绿色]和RP11-348I14(20q11.1-q11.21；德克萨斯红，光谱红）在4/104未培养的羊膜细胞中检测到20三体信号（3.8％），与正常对照组的0/100相比。使用从未培养的羊水细胞和亲本血液中提取的DNA进行的多态性DNA标记分析排除了单亲二体20。对母体血液的NIPT分析显示阴性结果，而20号染色体的基因剂量没有增加。怀孕一直持续到足月，健康的2830g女性婴儿分娩，无表型异常。脐带血和胎盘的核型均为46,XX。
结论：NIPT可用于羊膜穿刺术中20型镶嵌三体的假性镶嵌的快速鉴别诊断。
方法：33岁，初产妇在妊娠17周时接受了羊膜穿刺术，显示核型为47，XX，+20[8]/46,XX[31]。对从未培养的羊膜细胞中提取的DNA进行的同时阵列比较基因组杂交（aCGH）分析显示了arr（1-22，X）×2的结果，与基因组不平衡一致。在妊娠23周时，她被转诊到医院进行再次羊膜穿刺术。重复羊膜穿刺术时，培养的羊膜细胞核型为47，XX，+20[2]/46,XX[33]。亲本核型正常。使用SurePrintG3无限制CGHISCAv2，8×60K（AgilentTechnologies，圣克拉拉,CA,美国)没有发现基因组失衡，或ARR(1-22,X)×2,Y×0。使用RP11-266K16[20q13.33;异硫氰酸荧光素（FITC）的细菌人工染色体（BAC）探针进行间期荧光原位杂交（FISH）分析，光谱绿色]和RP11-348I14(20q11.1-q11.21；德克萨斯红，光谱红）在4/104未培养的羊膜细胞中检测到20三体信号（3.8％），与正常对照组的0/100相比。使用从未培养的羊水细胞和亲本血液中提取的DNA进行的多态性DNA标记分析排除了单亲二体20。对母体血液的NIPT分析显示阴性结果，而20号染色体的基因剂量没有增加。怀孕一直持续到足月，健康的2830g女性婴儿分娩，无表型异常。脐带血和胎盘的核型均为46,XX。
结论：NIPT可用于羊膜穿刺术中20型镶嵌三体的假性镶嵌的快速鉴别诊断。
