纤维蛋白原Ββ-链复合杂合突变导致的遗传性无纤维蛋白原血症

Inherited Afibrinogenemia Caused by Compound Heterozygous Mutations in the Β β-Chain of Fibrinogen

遗传性无纤维蛋白原血症是一种由于纤维蛋白原基因缺陷所致常染色体隐性遗传病。为了对1例遗传性无纤维蛋白原血症家系进行表型和基因型分析,采集了该家系三代10人外周血,吸取上层血浆用血凝仪检测活化部分凝血活酶时间(APTT)、凝血酶原时间(PT)和凝血酶时间(TT);纤维蛋白原(Fg)含量分别用Clauss法和免疫比浊法进行检测;以常规酚氯仿法抽提家系所有成员外周血基因组DNA,PCR扩增Fg基因FGA、FGB和FGG所有外显子及其侧翼序列和启动子区,PCR产物纯化后直接测序以检测基因突变。102例健康献血者作为正常对照。结果表明:先证者表型诊断为无纤维蛋白原血症;基因型呈FgΒβ链Arg17stop和Gly347Arg复合杂合突变,前者来源于母系,后者来源于父系。结论:FgΒβ链Arg17stop和Gly347Arg复合杂合突变是引起该家系先证者产生无纤维蛋白原血症的原因。

Congenital afibrinogenemia is a rare autosomal recessive disorder, characterized by the complete absence or extremely reduced level of fibrinogen. To analyze the phenotype and genotype of a family with inherited afibrinogenemia, laboratory studies including activated partial thromboplastin time （APTF） , prothrombin time （PT） and thrombin time （TT） were tested in the proband and 9 family members. Fibrinogen （Fg） in plasma were measured by both functional and immunoturbidimetry assay. All the exons, exon-intron boundaries and promoter regions of three Fg genes were analyzed by direct sequencing. 102 healthy blood donors were used as normal control. The results showed that phenotype of the proband was diagnosed as afibrinogenemia. Compound heterozygous mutations in Fg FGB gene were detected in the proband. One was a nonsense mutation（Arg17stop）in exon 2, traced back to the proband＇s mother. The other was a missense mutation （Gly347Arg） in exon 7, which was from the proband＇s father. It is concluded that afibrinogenemia is caused by the compound heterozygous mutations Arg17stop and Gly347Arg in the B β-chain of fibrinogen.