Department of Obstetrics and Gynecology, MacKay Memorial Hospital, Taipei, Taiwan; Department of Medical Research, MacKay Memorial Hospital, Taipei, Taiwan; School of Chinese Medicine, College of Chinese Medicine, China Medical University, Taichung, Taiwan; Institute of Clinical and Community Health Nursing, National Yang-Ming University, Taipei, Taiwan; Department of Obstetrics and Gynecology, School of Medicine, National Yang-Ming University, Taipei, Taiwan; Department of Medical Laboratory Science and Biotechnology, Asia University, Taichung, Taiwan.
Department of Obstetrics and Gynecology, Taipei Chang Gung Memorial Hospital, Taipei, Taiwan; College of Medicine, Chang Gung University, Taoyuan, Taiwan.
Taiwan J Obstet Gynecol. 2021 Mar;60(2):331-334. doi: 10.1016/j.tjog.2021.01.011.
We present prenatal diagnosis of low-level mosaicism for a small supernumerary marker chromosome (sSMC) derived from chromosome 9q (9q13-q21.33) in a pregnancy with a favorable outcome, and cytogenetic discrepancy between cultured amniocytes and uncultured amniocytes.
A 36-year-old, primigravid woman underwent amniocentesis at 17 weeks of gestation because of advanced maternal age. Cytogenetic analysis on cultured amniocytes revealed a karyotype of 46,XY in 20/20 colonies. Simultaneous array comparative genomic hybridization (aCGH) on the DNA extracted from uncultured amniocytes revealed 30% mosaicism for a de novo 20.3-Mb gene dosage increase at 9q13-q21.33. Repeat amniocentesis and cordocentesis were performed at 21 weeks of gestation. Cytogenetic analysis on cord blood revealed a karyotype of 47,XY,+mar [3]/46,XY [37]. aCGH analysis of cord blood revealed 7.5% mosaicism for a 17.15-Mb gene dosage increase at 9q21.11-q21.33. aCGH analysis of uncultured amniocytes revealed 11.7% mosaicism for a 17.15-Mb gene dosage increase at 9q21.11-q21.33. Polymorphic DNA marker analysis excluded uniparental disomy 9. The parental karyotypes were normal. The pregnancy was carried to 37 weeks of gestation, and a 2955-g phenotypically normal male baby was delivered. At birth, the cord blood had a karyotype of 47,XY,+mar [3]/46,XY [37], the placenta had a karyotype of 47,XY,+mar [10]/46,XY [30], and the umbilical cord had a karyotype of 47,XY,+mar [14]/46,XY [36]. aCGH analysis on the DNA extracted from cord blood at birth revealed no genomic imbalance. Interphase fluorescence in situ hybridization analysis on buccal mucosal cells at age two months detected 3.8% (4/106 cells) mosaicism for the sSMC, compared with 2% (2/100 cells) in the normal control. The neonate had normal physical development at age two months.
Cytogenetic discrepancy between cultured amniocytes and uncultured amniocytes may exist in the pregnancy with fetal mosaic sSMC. Low-level mosaicism for an sSMC derived from chromosome 9q13-q21.33 at prenatal diagnosis can be associated with a favorable outcome in the fetus.
我们报告了一例低水平嵌合体的产前诊断，该病例来源于染色体 9q（9q13-q21.33）的小额外标记染色体（sSMC），患者妊娠结局良好，且羊水细胞培养与未培养之间存在细胞遗传学差异。
一位 36 岁初产妇，因高龄接受了 17 周妊娠的羊膜穿刺术。对培养的羊水细胞进行细胞遗传学分析，在 20/20 个培养物中发现了 46,XY 核型。同时对未培养的羊水细胞进行 DNA 提取，使用微阵列比较基因组杂交（aCGH）检测到 9q13-q21.33 处存在 30%的新发 20.3-Mb 基因剂量增加的嵌合体。在 21 周妊娠时再次进行了羊膜穿刺术和脐带血穿刺术。对脐带血进行细胞遗传学分析，发现核型为 47,XY,+mar [3]/46,XY [37]。aCGH 分析显示 9q21.11-q21.33 处存在 7.5%的 17.15-Mb 基因剂量增加的嵌合体。未培养的羊水细胞 aCGH 分析显示 9q21.11-q21.33 处存在 11.7%的 17.15-Mb 基因剂量增加的嵌合体。多态性 DNA 标记分析排除了 9 号染色体单亲二体。父母的核型正常。妊娠持续至 37 周，分娩出一名 2955g 表型正常的男婴。出生时，脐带血核型为 47,XY,+mar [3]/46,XY [37]，胎盘核型为 47,XY,+mar [10]/46,XY [30]，脐带核型为 47,XY,+mar [14]/46,XY [36]。出生时脐带血提取的 DNA 进行 aCGH 分析，未发现基因组失衡。2 月龄时颊黏膜细胞的间期荧光原位杂交分析显示，sSMC 的嵌合体为 3.8%（4/106 个细胞），而正常对照组为 2%（2/100 个细胞）。2 月龄时，新生儿的体格发育正常。
在胎儿存在 sSMC 的嵌合体妊娠中，羊水细胞培养与未培养之间可能存在细胞遗传学差异。产前诊断中低水平的 9q13-q21.33 来源的 sSMC 嵌合体可能与胎儿良好的结局相关。
