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

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.