One case of pseudomosaic trisomy 20 prenatally diagnosed by amniocentesis at second trimester / 中华围产医学杂志

ABSTRACT

Objective To investigate the prenatal diagnosis and prenatal genetic conselling of pseudomosaic trisomy 20. Methods One case of pseudomosaic trisomy 20 was analyzed and relative literatures were reviewed. Results A 31-year-old gravid 1, para 0 woman underwent amniocentesis at 18 weeks of gestation due to high risk of trisomy 21 during maternal serum screening in September, 2012. Interphase fluorescence in situ hybridization (FISH) of amniocytes with probes GLP13/GLP21/CSP18/CSPX/CSPY showed a normal result, while cytogenetic analysis of cultured amniocytes revealed a karyotype of 47,XY,+20[7]/46,XY[9]. The level of trisomy in the cultured amniocytes was 7/16. Cordocentesis revealed a karyotype of 46,XY in cultured cord blood cells. Interphase FISH analysis was performed using the probes D20Z1 (20p11.1-q11.1) and D20S1157/20QTEL14 (20 per/qter). Each probe showed two signals in all uncultured amniocytes. The prenatal ultrasound findings were unremarkable. The mosaicism was considered to be pseudomosaicism. After genetic counseling, the parents selected to continue the pregnancy. A healthy male baby was delivered at 39 weeks of gestation. Postnatal cytogenetic analysis revealed a karyotype of 46,XY in peripheral blood lymphocytes. Interphase FISH analysis of the uncultured buccal cast-off cells using the probes D20Z1 and D20S1157/20QTEL14 showed normal results in 100%cells. There was no phenotypic abnormality at the age of seven months. Conclusions When mosaic trisomy 20 is identified in amniocytes, further evaluation and genetic counseling are required. Interphase FISH of the uncultured amniocytes with a chromosome-specific probe is a useful tool for confirmation of the prenatal diagnosis of mosaicism. Genetic analysis of multiple tissues is required postnatally.