OBJECTIVE To carry out prenatal diagnosis for a fetus with absent nasal bone by using cytogenetic and molecular techniques. METHODS Chromosomal karyotyping, single nucleotide polymorphism array (SNP-array) and fluorescence in situ hybridization (FISH) assays were applied for the diagnoses. Peripheral blood samples were also taken from the parents for chromosomal karyotyping and FISH analysis. RESULTS The fetus was found to have a 46,XX,add(21)(p11.2) karyotype, and SNP-array has revealed a 11.3 Mb duplication at 21q22.12q22.3 (hg19: 36 762 648-48 093 361), which was confirmed by FISH. Both parents were found to be normal by chromosomal karyotyping and FISH analysis. The fetus was ultimately found to have a karyotype of 46,XX,der(21)t(21;21)(p11.2;q22.1), resulting a de novo partial trisomy of 21q22.1. CONCLUSION Combined use of various techniques has enabled accurate prenatal diagnosis and genetic counseling for the fetus.

中文翻译：

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一例罕见的新生部分21q(21q22.1→ qter)三体综合征伴鼻骨缺如的产前诊断[J].

目的应用细胞遗传学和分子学技术对鼻骨缺失胎儿进行产前诊断。方法染色体核型分析、单核苷酸多态性阵列（SNP-array）和荧光原位杂交（FISH）检测用于诊断。外周血样本也取自父母，用于染色体核型分析和 FISH 分析。结果 发现胎儿有 46,XX,add(21)(p11.2) 核型，SNP 阵列显示 21q22.12q22.3 (hg19: 36 762 648-48 093 361) 有 11.3 Mb 重复，这得到了 FISH 的证实。通过染色体核型分析和 FISH 分析发现父母双方都正常。最终发现胎儿的核型为 46,XX,der(21)t(21;21)(p11.2;q22.1)，导致 21q22.1 从头部分三体。