Clinical features and genetic analysis of two fetuses with ring chromosome 21 mosaicism
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目的 探讨2例21号环状染色体嵌合体胎儿的围产期临床表型和遗传学特征。 方法 选取2021年11月在厦门市妇幼保健院接受介入性产前诊断的2例胎儿为研究对象。收集2例胎儿的临床资料，应用常规G显带核型分析和染色体微阵列分析(CMA)对2例胎儿及其父母进行遗传学检测。 结果 胎儿1超声提示胎儿鼻骨未显示、室间隔缺损、永存左上腔静脉、三尖瓣轻度返流，染色体核型结果为46，X？，dic r(21；21)(p12q22；q22p12)[41]/45，X？，-21[9]，CMA检测结果提示其染色体21q11.2q22.3区存在30.00 Mb片段的4拷贝，21q22.3区存在3.00 Mb片段的缺失。胎儿2超声提示鼻骨呈点状回声，核型为46，X？，r(21)(p12q22)[83]/45，X？，-21[14]/46，X？，dic r(21；21)(p12q22；q22p12)[3]，CMA结果提示其染色体21q22.12q22.3区存在5.10 Mb片段的4拷贝，21q22.3区存在2.30 Mb片段的缺失。 结论 2例21号环状染色体嵌合体的围产期表型与靠近染色体缺失断裂位点处的染色体片段重复相关，染色体核型分析联合CMA对于环状染色体的产前诊断和遗传咨询具有指导意义。 Objective To investigate the perinatal clinical phenotype and genetic characteristics of two fetuses with ring chromosome 21 mosaicisms. Methods Two fetuses who were diagnosed at the Xiamen Maternal and Child Health Care Hospital in November 2021 were selected as the study subjects. Clinical data of the two fetuses were collected. Conventional G-banded karyotyping and chromosomal microarray analysis (CMA) were carried out for the fetuses and their parents. Results Prenatal ultrasonography of fetus 1 has revealed absence of nasal bone, ventricular septal defect, persistent left superior vena cava, and mild tricuspid regurgitation. Chromosomal karyotyping was 46, X?, dic r(21 21)(p12q22 q22p12)[41]/45, X?, -21[9]. CMA has revealed a 30.00 Mb quadruplication at 21q11.2q22.3 and a 3.00 Mb deletion at 21q22.3. For fetus 2, ultrasonography has revealed pointed echo of the nasal bone. The fetus was found to have a karyotype of 46, X?, r(21)(p12q22)[83]/45, X?, -21[14]/46, X?, dic r(21 21)(p12q22 q22p12)[3]. CMA has revealed a 5.10 Mb quadruplication at 21q22.12q22.3 and a 2.30 Mb deletion at 21q22.3. Conclusion The perinatal phenotype of the two fetuses with ring chromosome 21 mosaicisms is related to the duplication of chromosomal segments near the breakpoints of the chromosomal deletions. The combined chromosomal karyotyping and CMA has enabled prenatal diagnosis and genetic counseling for these families.
Objective To investigate the perinatal clinical phenotype and genetic characteristics of two fetuses with ring chromosome 21 mosaicisms. Methods Two fetuses who were diagnosed at the Xiamen Maternal and Child Health Care Hospital in November 2021 were selected as the study subjects. Clinical data of the two fetuses were collected. Conventional G-banded karyotyping and chromosomal microarray analysis (CMA) were carried out for the fetuses and their parents. Results Prenatal ultrasonography of fetus 1 has revealed absence of nasal bone, ventricular septal defect, persistent left superior vena cava, and mild tricuspid regurgitation. Chromosomal karyotyping was 46, X?, dic r(21 21)(p12q22 q22p12)[41]/45, X?, -21[9]. CMA has revealed a 30.00 Mb quadruplication at 21q11.2q22.3 and a 3.00 Mb deletion at 21q22.3. For fetus 2, ultrasonography has revealed pointed echo of the nasal bone. The fetus was found to have a karyotype of 46, X?, r(21)(p12q22)[83]/45, X?, -21[14]/46, X?, dic r(21 21)(p12q22 q22p12)[3]. CMA has revealed a 5.10 Mb quadruplication at 21q22.12q22.3 and a 2.30 Mb deletion at 21q22.3. Conclusion The perinatal phenotype of the two fetuses with ring chromosome 21 mosaicisms is related to the duplication of chromosomal segments near the breakpoints of the chromosomal deletions. The combined chromosomal karyotyping and CMA has enabled prenatal diagnosis and genetic counseling for these families.
Ring chromosomeMosaicismMicroduplication/microdeletionGeneticsPrenatal diagnosis
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