[Prenatal diagnosis of five cases of monochorionic-diamniotic twins discordant for karyotype analysis].

Zhonghua yi xue yi chuan xue za zhi = Zhonghua yixue yichuanxue zazhi = Chinese journal of medical genetics

PubMedID: 26418994

Wu J, Zhou Y, Lin S, Chen B, Xie Y. [Prenatal diagnosis of five cases of monochorionic-diamniotic twins discordant for karyotype analysis]. Zhonghua Yi Xue Yi Chuan Xue Za Zhi. 2015;32(5):691-4.
OBJECTIVE
To explore the mechanism and diagnostic method for monochorionic-diamniotic twins discordant for karyotype analysis.

METHODS
Dual amniocentesis was performed on five pairs of monochorionic-diamniotic twins, which all consisted of a normal twin and one with multiple malformations revealed by ultrasound.Karyotype analysis was performed on amniocytes derived from each of the twins. Zygosity was also determined with DNA extracted from amniocytes with 16 polymorphic microsatellite markers.

RESULTS
Three cases of 45,X, one case of 47,XX,+9 and one case of 47,XY,+18 were detected among the abnormal twins, while the normal fetuses all had a normal karyotype.DNA analysis suggested that, in all cases, the twins have shared the 16 polymorphic microsatellite markers, which confirmed their monozygosity.

CONCLUSION
Monochorionic-diamniotic twins may be discordant for karyotyping, for which anaphase lagging, chromosomal non-disjunction and trisomy rescue may be the underlying reasons.As a simple method, dual amniocentesis can be used to obtain amniotic fluid samples for karyotype analysis and determination of zygosity for such twins.