ABSTRACT Objective This study conducted a comparative analysis of chromosomal karyotyping, SNP‐array, and FISH results in 82 prenatal cases of mosaicism involving the sex chromosomes. Methods A retrospective analysis was conducted on 82 cases of mosaicism involving the sex chromosomes; the analysis focused on the concordance and discrepancies among karyotyping, SNP‐array, and FISH results. Results Among 10,825 high‐risk pregnancies undergoing amniocentesis, 82 cases (0.76%) of mosaicism involving the sex chromosomes were detected. These included 60 cases (73.2%) of X or Y chromosome aneuploidy mosaicism and 22 cases (26.8%) with mosaicism accompanied by structural abnormalities. Of the 82 cases, 64 showed consistent results across karyotyping, SNP‐array, and FISH, while 18 cases exhibited discrepancies between methods. Among the 18 discordant cases, 12 were diagnosed as mosaicism by karyotyping and FISH but showed normal results on SNP‐array. SNP‐array identified three additional cases of mosaic X chromosome copy number variations (CNVs). In three cases, Turner mosaicism was diagnosed solely by FISH; both karyotype and SNP‐array findings were normal. Conclusions This study demonstrates that the combination of SNP‐array, karyotyping, and FISH can effectively diagnose mosaicism involving the sex chromosomes. Karyotype analysis can effectively identify aneuploidy and balanced translocation mosaicism when X chromosome dosage shows no significant change, whereas SNP array is more effective in detecting mosaic copy number variations < 10 Mb. In cases of discrepant results between the two methods, FISH should be utilized for further verification.
Luo et al. (Fri,) studied this question.