Mosaic tetrasomy 9p detected by CNV-seq but missed by traditional karyotyping in a prenatal case without dysmorphic features

Molecular Cytogenetics · Published 2025-07-14 · DOI 10.1186/s13039-025-00720-9

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Abstract

Abstract Introduction A unique case of mosaic tetrasomy 9p was found using CNV-seq analysis of uncultured amniocytes, which was missed by karyotype analysis of cultured amniocytes. Case report The karyotype was determined to be 46, XY, with mosaic duplication of chromosome 9 from p24.3 to p13.1 indicated by CNV sequencing in the initial amniocentesis. Subsequent prenatal testing revealed a normal karyotype, with FISH analysis of cultured amniocytes identifying 2% tetrasomy of chromosome 9p. The karyotype of cord blood revealed mosaic tetrasomy 9p, while CNV-seq on uncultured cord blood indicated nearly complete tetrasomy 9p. Conclusions It is recommended to conduct CNV-seq or CMA on uncultured amniocytes in conjunction with karyotype analysis on cultured amniocytes. The presence of mosaic tetrasomy 9p during amniocentesis may result in either a benign condition or an adverse outcome, necessitating informed decision-making for pregnant women facing such circumstances.

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Publication details

Year
2025

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