METHODS: Amniotic fluid cells were extracted from pregnant woman and sent for karyotype and chromosomal microarray analysis (CMA). Trio pedigree analysis was conducted with Chromosome Analysis Suite and uniparental disomy (UPD)-tool software.
RESULTS: CMA identified consistent results, which were 2 regions of homozygosity: arr[GRCh37]20p12.2q11.1 (11265096_26266313)hmz and arr[GRCh37]20q11.21q13.2(29510306_54430467)hmz. The trio pedigree analysis discovered that the fetal chromosome 20 was the entire maternal UPD mosaic with isodisomy and heterodisomy.
CONCLUSIONS: When a large segment of chromosome is homozygous, appropriate genetic tests are required to find the potential mechanisms for UPD formation.
方法:从孕妇中提取羊水细胞,并送去进行核型和染色体微阵列分析(CMA)。使用染色体分析套件和单亲二体(UPD)工具软件进行三人系谱分析。
结果:CMA确定了一致的结果,它们是2个纯合性区域:ARR[GRCh37]20p12.2q11.1(11265096_26266313)hmz和ARR[GRCh37]20q11.21q13.2(29510306_54430467)hmz。三人系谱分析发现,胎儿20号染色体是具有等体性和异体性的整个母体UPD马赛克。
结论:当染色体的大部分是纯合的,需要进行适当的基因测试以发现UPD形成的潜在机制。