Objective To compare the value of single nucleotide polymorphism array(SNP-array),fluorescence in situ hybridization(FISH)and karyotype analysis in prenatal diagnosis of a fetus with structural abnormality of Y chromosome.Methods A high-risk case with a reduced number of sex chromosomes is indicated by noninvasive prenatal screening(NIPT).Rapid molecular diagnosis of aneuploidy,single nucleotide polymorphism array(SNP-array)and karyotyping were conducted.Fluorescence in situ hybridization(FISH)was performed to clarify the results after the results of three methods were not com-pletely consistent.Results The results of rapid aneuploidy molecular diagnosis suggested one X chromosome signal and the two Y chromosome signals,and the SNP-array results showed Yq11.221q11.23x0 and Yp1 1.31q1 1.221x2,suggesting that the Y chromosome was missing part of its long arm,with the size of 12.54 Mb,and the missing fragments were mainly related to the spermatogonial function of the AZFb+c region.The karyotype analysis results are:mos 46,X,psu idic(Y)(q11.221)[62]/46,X,del(Y)(q11.221)[8],indicating the fetus is a mosaic with an isodicentric Y chromosome with pseudoautosomal region and a deletion of the long arm fragment of chromosome Y,consistent with the breakpoints indicated by the SNP-array.Further FISH testing on fetal amniotic fluid interphase and metaphase cells showed:(DYZ3)X1[30]/(DYZ3)X2[70],suggesting a mosaicism with structural abnormalities of the Y chromosome in the fetus.Conclusion For fetuses with NIPT suggestive of sex chromo-some abnormalities,it is recommended that multiple genetic tests be used in combination to accurately detect sex chromosome structural abnormalities and exclude the presence of chimerism,which can provide more accurate information for genetic counseling.
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