摘要目的 对1个姨表近亲结婚的遗传性凝血因子Ⅴ (coagulation factor Ⅴ,FⅤ)缺陷症家系进行基因分析,探讨其分子发病机制.方法 检测先证者及其家系成员的凝血酶原时间(prothrombin time,PT)、活化部分凝血活酶时间(activated partial thromboplastin time,APTT)、纤维蛋白原(fibrinogen,FIB)、血浆FⅤ活性(FⅤ∶C)和血浆FⅤ抗原(FⅤ∶Ag)等凝血指标进行表型诊断.用DNA直接测序法分析先证者及家系成员F5基因的全部外显子及侧翼、5’和3’非翻译区,发现突变位点用反向测序予以证实.结果 先证者PT和APTT均明显延长,分别为23.5s和50.5s,其FⅤ∶C(8％)和FⅤ∶Ag(＜1％)极度减低；同样先证者的妹妹PT和APTT也显著延长,分别为24.1s和62.4 s,其FⅤ∶C(7％)和FⅤ；Ag(＜1％)也极度减低；家系其他成员的PT及APTT均在正常参考范围.先证者的F5基因第5外显子测序发现其29170位为纯合突变T→C,导致190位氨基酸苯丙氨酸变为丝氨酸(Phe190Ser),先证者的妹妹同样为纯合Phe190Ser突变；大哥、大姐、大女儿、小女儿和外甥女均为Phe190Ser杂合突变,其FⅤ∶C也有所减低(分别为57％、73％、72％、66％、75％)；两个弟弟为正常野生型,其FⅤ∶C和FⅤ∶Ag均在正常水平.结论 该遗传性FⅤ缺陷症家系先证者及其妹妹F5基因第5外显子存在g.29170T→C纯合型错义突变,导致Phe190Ser.其原因推测与其父母近亲结婚有关.Phe190Ser与该遗传性凝血因子Ⅴ缺陷症家系FⅤ水平降低有关.

abstractsObjective To screen potential mutation and explore the underlying mechanism for a consanguineous pedigree featuring hereditary coagulation factor Ⅴ (F Ⅴ) deficiency.Methods Clinical diagnosis was validated by coagulant parameter assays of prothrombin time (PT),activated partial thromboplastin time (APTT),fibrinogen (FIB),FⅤ procoagulant activity (FⅤ ∶ C) and FⅤ antigen (FⅤ:Ag).Potential mutations of the F5 gene in the proband and his family members were analyzed by direct DNA sequencing of PCR products of all exons,exon-intron boundaries and 3',5' untranslated regions.Suspected mutation was confirmed by reverse sequencing.Results The PT and APTT in the proband were significantly prolonged,which measured 23.5 s (reference range 11.8-14.8 s) and 50.5 s (reference range 27.0-41.0 s),respectively.FⅤ activity and FⅤ antigen of the proband were significantly reduced to 8％ and ＜ 1％,respectively.PT and APTT in the younger sister of the proband were also significantly prolonged (24.1 s and 62.4 s,respectively).Her FⅤ activity and FⅤ antigen were also significantly decreased (7％ and ＜ 1％,respectively).PT and APTT of other family members were within normal range.The homozygous missence mutation causing T→C transition at position 29 170 in exon 5 of F5 gene has resulted in a Phe190Ser substitution in the proband.His younger sister was also homozygous for Phe190Ser.Heterozygosity for Phe190Ser was confirmed in his elder brother,elder sister,two daughters and niece,and their FⅤ activity were slightly decreased (57％ 、73％ 、72％ 、66％ and 75％,respectively).A normal wild type was observed in two younger brothers of the proband,and their F Ⅴ activity and F Ⅴ antigen were in the normal range.Conclusion Homozygous missence mutation of Phe190Ser has been found in above family featuring hereditary FⅤ deficiency.The homozygous missence mutation was inherited from the parents by consanguineous marriage.Phe190Ser probably underlies may underlie the pathogenesis of hereditary factor Ⅴ deficiency in this pedigree.