胎儿甲型血友病的基因诊断

Prenatal diagnosis for fetus with hemophilia A

目的探讨胎儿甲型血友病的产前基因诊断方法的临床应用价值。方法2002年1月至2006年12月对北京朝阳医院妇产科19个甲型血友病家系进行基因携带者检测，应用长距离PCR（LD-PCR）技术检测其凝血因子Ⅷ（FⅧ）内含子22倒位情况，出现倒位者直接行脐静脉穿刺抽取脐带血进行胎儿血友病基因的产前诊断；非倒位者则联合应用多位点基因连锁分析技术先对携带者进行筛查，而后进行胎儿血友病基因的产前诊断。同时进行胎儿脐带血FⅧ水平的检测。结果（1）对19例孕妇的22次妊娠的胎儿进行了产前诊断，平均脐静脉穿刺孕周为23周（17～34周），所有穿刺均获成功，无穿刺导致的胎儿丢失。（2）19个甲型血友病家系中，有14个家系检测出内含子22倒位，对其16次妊娠胎儿行产前甲型血友病基因诊断，其中10例胎儿诊断为甲型血友病；6例诊断为正常胎儿。（3）多位点基因连锁分析技术产前诊断甲型血友病胎儿6例，其中包括1例孕妇先后2次妊娠甲型血友病胎儿。（4）22例胎儿中有16例进行了FⅧ水平检测（未行检测的6例为孕周低于20周或因经济原因患者家属拒绝），FⅧ水平在0～198％之间，有11例胎儿FⅧ水平〈10％，其中除1例FⅧ水平为2％，诊断为正常胎儿并随访1年FⅧ水平正常外，其余10例胎儿均诊断为甲型血友病。结论应用LD．PCR和多位点基因连锁分析技术可以快速有效地进行甲型血友病携带者的确认；胎儿脐带血FⅧ水平的检测有助于初步诊断，但确诊胎儿是否患病仍须有基因诊断结果。

Objective To study the prenatal genetic diagnostic methods for hemophilia A fetus. Methods From 2002 to 2006, 19 hemophilia A families were diagnosed either by long distanee-polymerase chain reaction （LD-PCR） for factor Ⅷ intron 22 inversion or by the DNA polymorphism genetic linkage analysis of factor Ⅷ in the Beijing Chaoyang Hospital. Results （1） Totally 19 women, with 22 pregnancies received the prenatal diagnosis of fetal hemophilia A. The average week at diagnosis was 23 （17- 34 ） weeks. All the direct fetal blood sampling （DFBS） were successful. There was no fetal-loss caused by the procedures. （2） Of the 19 hemophilia A families, 14 appeared to be factor Ⅷ intron 22 inversion, in which 16 prenatal diagnoses were done, 10 fetuses were diagnosed as genetieal hemophilia A patients, and 6 fetuses were normal. （3） Using combined polymorphism genetic linkage analysis 6 prenatal diagnoses were done, including one woman＇s two pregnancies, in which both her fetuses were diagnosed as genetieal hemophilia A patients. （4） Factor Ⅷ levels of 16 fetuses were measured, and 6 fetuses were unmeasured either because the pregnancy weeks were lower than 20 weeks or the parents refused. Factor Ⅷ level ranged from 0 to 198%. There were 11 fetuses whose factor Ⅷ levels were lower than 10%. Ten of them were diagnosed to be genetieal hemophilia A patients, and in only one boy the factor Ⅷ level was 2% , but the genetic diagnosis was normal and for one year＇s follow up he was doing normal. Conclusion LDPCR combined with polymorphism genetic linkage analysis enables a quick and correct detection of hemophilia A carrier. For a carrier pregnancy, prenatal diagnosis could be done for the male fetus. Factor Ⅷ deficiency of the fetus could help make the diagnosis but the final diagnosis should be based on genetic evidence.