Misdiagnosis of mosaic tetrasomy 9p in a fetus by single nucleotide polymorphism-based array / 中华医学遗传学杂志

ABSTRACT

<p><b>OBJECTIVE</b>To explore the reason for discordant results of karyotyping and microarray analysis in a fetus with mosaic tetrasomy 9p.</p><p><b>METHODS</b>Amniocentesis was carried out for a pregnant woman with advanced age for whom ultrasound scan has indicated fetal ventricular expansion, intrauterine growth retardation and persistent upper venous cavity. G-banded karyotyping and single nucleotide polymorphism-based arrays (SNP-array) analysis were performed at the same time.</p><p><b>RESULTS</b>Analysis of amniocytic chromosome has suggested mosaic tetrasomy 9p (47,XX,+psu idic(9)(q21)[23]/46,XX[27]). While SNP-array has detected a non-mosaic trisomy 9p with a 68.7 Mb duplication at 9p24.3q21.11. The results of the two methods were therefore discordant.</p><p><b>CONCLUSION</b>SNP-array will analyze genetic material in the form of numbers rather than morphology. For chimeras containing two types of cell lines, when the mosaic rate was close to 50% and the average amount of genetic material of the chimeras was equivalent to the amount of genetic material of non-chimeras, microarray analysis may come to the conclusion of a non-mosaic heteroploidy. Therefore, microarray results for large segment chromosome abnormalities should be combined with the results of G-banded karyotyping for genetic counseling.</p>