Genetic Analysis of Second Pregnancy with A Child of 21-Trisomy Syndrome in A Phenotypically Normal Mother
LIU Guo-zhong
HOU Hai-yan
CHANG Yu
HAO Chun-xia
SUI Li-ting
Abstract：The repeated pregnancies with 21-trisomy syndrome in a phenotypically normal mother are rare,and the possibility of maternal chromosomal mosaic should be considered.We report a woman with normal phenotype who had a history of early embryo loss for 4 times,two of which the karyotypes were 47,XY,+21.The couple's karyotypes were normal(counting 20 split phases).Both noninvasive prenatal testing(NIPT)and extended NIPT results refer to a high risk of trisomy 21,and the amniocentesis single nucleotide polymorphism array(SNP-array)result was[arr(1-22)×2,(XN×1)],and the fetal amniotic fluid karyotype was 46,XN.The repeated peripheral blood chromosomes test for the couple(counting 50 split phases)was performed,the maternal chromosome karyotype was diagnosed as 47,XX,+21[4]/46,XX[46],with a mosaic ratio of 7％-8％.Maternal fluorescence in situ hybridization(FISH)assay in 100 counted cells showed 7 trisomy 21 cells,suggesting that 7％of the cells were trisomy 21.Fetal amniotic fluid FISH test found no 21-trisomy cell.A healthy baby girl was delivered by cesarean section at 40+1 weeks of gestation.In this case,maternal karyotype of a mosaic 21-trisomy cell/normal cell phenotype may contribute to the twice early pregnancy losses with 21-trisomy syndrome.
Keywords：Down syndromeTrisomyChimeraGenetic counselingKaryotypingIn situ hybridizationfluorescence
Publication Date：2024-07-15
Online Publishing Date：2025-08-15(First online date of this platform, not the publication date of the document)
Pages：5( 305-308,327 )