Zhu Yuying, Wu Ke, Jiang Cuicui, Zhu Qiumin
Prenatal Diagnosis Center, Quzhou Maternal and Child Healthcare Hospital, Quzhou, Zhejiang, China.
Laboratory of Prenatal Diagnosis Center, Quzhou Maternal and Child Healthcare Hospital, Quzhou, Zhejiang, China.
Front Genet. 2025 Mar 5;16:1544565. doi: 10.3389/fgene.2025.1544565. eCollection 2025.
Uniparental disomy (UPD) occurs when both homologous chromosomes are inherited from a single parent. To date, the UPD of all autosomes and the X chromosome has been recorded. A few cases of UPD of chromosome 21 have been documented. At 15 weeks of gestation, a 25-year-old pregnant woman's non-invasive prenatal screening revealed a high risk of trisomy 21. Although no anomalies were detected in the fetal ultrasonography, amniocentesis was performed, and the fetal karyotype analysis was found normal. A single-nucleotide polymorphism (SNP) array revealed that the fetus had the copy-neutral region of homozygosity (ROH) in the long arm of chromosome 21. Subsequently, single whole-exome sequencing was performed due to the risk of recessive gene variants in ROH, and no homozygous like pathogenic or pathogenic variants were found on the long arm of chromosome 21. After genetic counseling, the parents decided to continue this pregnancy. At 37 weeks of gestation, a live male infant was delivered by Cesarean section. Copy number variation sequencing showed that the placental tissue was mosaic for trisomy 21. At the final follow-up evaluation, the 6-month-old boy had a normal phenotype.
单亲二体（UPD）是指两条同源染色体均来自单一亲本。迄今为止，已记录了所有常染色体和X染色体的UPD情况。已记录了少数21号染色体UPD的病例。妊娠15周时，一名25岁孕妇的无创产前筛查显示21三体风险高。尽管胎儿超声检查未发现异常，但仍进行了羊膜穿刺术，胎儿核型分析结果正常。单核苷酸多态性（SNP）阵列显示胎儿21号染色体长臂存在纯合性拷贝中性区域（ROH）。随后，由于ROH中存在隐性基因变异风险，进行了单全外显子测序，在21号染色体长臂上未发现纯合样致病或致病变异。经过遗传咨询，父母决定继续妊娠。妊娠37周时，通过剖宫产分娩出一名活男婴。拷贝数变异测序显示胎盘组织为21三体嵌合体。在最后的随访评估中，这个6个月大的男孩表型正常。
