Prenatal Diagnosis of 47,XYY Syndrome:Report of Two Cases

　　　　　背景：產前能夠診斷47,XYY往往是因高齡產婦作染色體檢查才得知。本篇報告兩 病例:一例是作產前母血唐氏症篩檢異常，一例是母血甲型胎兒蛋白偏低，進而作染色體檢 查，證實為47,XYY。 病例報告：病例1，一位33歲經產婦，在妊娠17週時接受唐氏症篩檢，發現母血甲型 胎兒蛋白偏低(0.48MoM)。羊水染色體檢查結果為47,XYY，孕婦決定終止妊娠。病例2，一位 34歲經產婦，妊娠20週時在外院接受唐氏症篩檢，其危險機率偏高(1:48)，羊水檢查發現 為47,XYY，於妊娠24週轉至本院，要求作進一步確認。作者抽取胎兒臍帶血，並利用螢光 原位雜合法快速診斷出此一種染色體異常。由於超音波並未發現有明顯結構缺陷，孕婦決定 繼續妊娠，並於足月自然娩出一正常男嬰。 結論：47,XYY胎兒若無明顯結構異常，孕婦可考慮繼續妊娠到足月並娩出嬰兒。此外， 螢光原位雜合法可在一個工作天內快速診斷出染色體數目異常。
　　　　　Background: Prenatal diagnosis of 47,XYY syndrome has been made only occasionally, usually as a result of genetic screening due to advanced maternal age. We present two cases of this syndrome, which were detected due to low maternal serum alpha-fetoprotein or positive maternal serum screening for Down syndrome. Case report: Case 1, a 33-year-old multipara underwent maternal serum screening for Down syndrome at 17 weeks' gestation. A low maternal serum AFP level with 0.48 multiples of the median and a Down Syndrome risk of 1:347 were disclosed. Amniocentesis for chromosome analysis showed a karyotype of 47,XYY. Termination of the pregnancy was elected by the mother. Case 2, a 34-year-old multipara, also received a Down syndrome screening test at 20 weeks' gestation at a local clinic. The risk of Down syndrome was high, 1:48. Cordocentesis was done at 24 weeks of gestation at our hospital. Interphase fluorescence in situ hybridization (FISH) was performed on uncultured lymphocytes for a quick analysis. The mother decided to continue with the pregnancy and a normal baby was born at term. Conclusion: If there are no significant abnormalities found on ultrasound, a pregnancy with a 47,XYY karyotype fetus might be continued and the birth of a grossly normal baby might be expected. Additionally, interphase FISH can provide a quick determination of the exact number of copies of chromosomes in less than one day.