[Prenatal diagnosis and genetic analysis of a fetus with mosaicism 3q26-qter duplication and 10q26-qter deletion].

OBJECTIVE: To analyze a fetus with a mosaicism unbalanced chromosomal translocation and explore its genetic mechanism and potential risks. METHODS: A pregnant woman undergoing prenatal diagnosis at Peking University Shenzhen Hospital due to high-risk by Down syndrome screening was selected as study subject. With informed consent obtained, karyotyping analysis and chromosomal microarray analysis (CMA) were conducted on amniotic fluid cells and peripheral blood samples from the couple. Fluorescence in situ hybridization (FISH) was also performed on sperm sample from the husband. This study was approved by the Medical Ethics Committee of the hospital (Ethics No.: 2026-032). RESULTS: Karyotyping analysis of amniotic fluid cells indicated a derivative chromosome 10, der(10)t(3;10), with a mosaicism level of 20%. CMA revealed a duplication of 3q26.32-q29 (mosaicism rate: 17%) and a deletion of 10q26.12-q26.3 (mosaicism rate: 18%). The karyotyping and CMA results of the couple were both normal. FISH analysis of the sperm did not detect signals for 3q27.3 duplication and 10q26.3 deletion. CONCLUSION: The mosaicism unbalanced chromosomal translocation in the fetus is a de novo rearrangement, and its phenotype exhibited heterogeneity.