临床不同背景情况下血友病A的产前诊断方案

目的建立临床不同背景情况下HA患儿产前诊断方案.方法对前来要求作HA产前诊断的15例孕妇进行遗传咨询,根据孕周和临床资料不同采取不同诊断方法.孕妇孕周＜23周,有先证者且已明确基因突变类型,抽羊水进行直接基因诊断和间接遗传连锁分析;有先证者但未明确基因突变类型,抽脐血进行间接遗传连锁分析和FⅧ活性检测;孕妇孕周＞23周且无先证者,抽脐血做FⅧ活性检测和性别染色体检查,但不能诊断携带者.直接基因诊断采用长距离PCR技术,对F8基因内含子22和内含子1倒位进行检测,找不到倒位者,行核苷酸测序;连锁分析采用F8基因内外的7个位点(DXS1108,F8Civs13,INTRON22,DXS1073,DXS9901,DXS15,DXS8069)以及性别位点(Amelo).产前诊断标本均需做母血污染鉴定.结果 15例产前诊断标本均无母血污染.明确诊断血友病A胎儿5例,其中脐血FⅧ活性＜1%的3例,1例伴21三体;F8基因22内含子倒位1例;F8基因23外显子错义突变p.Arg2182Cys 1例.结论对临床不同背景情况下采取不同方案进行HA产前诊断,可提高HA患儿检出率和准确性,最大程度地预防出生缺陷儿的发生.

Prenatal diagnosis strategy of hemophilia A with different clinical backgrounds

Objective To prenatally diagnose HA fetus with different clinical backgrounds. Methods Genetic tests were performed on 15 gravidas subjected for prenatal diagnosis of HA and different methods were employed for diagnosis according to the gestational weeks and clinical data. Amniotic fluid were taken from pregnant women within 23 gestational weeks for direct genotyping and indirect linkage analysis, since these women had probands with clear-cut mutations. Cordocentesis was performed for linkage analysis in pregnant women over 23 gestational weeks with probands whose types of mutation were unknown, while the FⅧ activity tests were carried out simultaneously. For the pregnant women over 23 gestational weeks without proband, cordocentesis was operated for measurement of FⅧ activity and karyotyping, but carriers of hemophilia A could not be detected in these cases. The introns 22 and 1 inversion of F8 gene were identified by long distance-polymerase chain reaction. Nucleotide sequencing was employed if the gene inversion could not be found and linkage analysis of 7 polymorphic markers, including DXS1108, F8Civs13, INTRON22,DXS1073,DXS9901, DXS15, DXS8069 and sex site (Amelo) were applied eventually. Identification of maternal blood contamination must be done before the tests. Results Fifteen samples were identified without maternal blood contamination. Five fetuses were diagnosed with hemophilia A. Meanwhile there were three pregnant women whose cord blood FⅧ activities were less than 1%. One of them was accompanied by trisomy 21; another had inversion mutation in introns 22 of F8 gene; the remaining one was identified with missense mutation in exon 23 (p. Arg2182Cys) of F8 gene. Conclusions Diverse methods should be applied in prenatal diagnosis of hemophilia A with different clinical backgrounds, for the sake of birth defects prevention.