[The analysis of a pedigree with hereditary coagulation factor Ⅴ deficiency caused by compound heterozygous variation of F5 gene].

Objective: To analyze the gene variation of a genetic coagulation factor Ⅴ (FⅤ) deficiency pedigree and explore the molecular pathogenesis. Methods: The proband was a 32 years old female. The patient was prone to nose bleeding since childhood which was usually self-healed. On March 10, 2021, the proband went to the First Affiliated Hospital of Air Force Medical University for treatment of knee hematoma caused by a fall. None of the family members reported any history of bleeding. The prothrombin time (PT), activated partial thromboplastin time (APTT) and FⅤ activity (FⅤ: C) were detected by clotting method and the FⅤ antigen (FⅤ: Ag) was tested with enzyme-linked immunosorbent assay (ELISA). All exons and flanks of F5 gene were determined by Sanger sequencing. Clustalx-2.1-win, PolyPhen-2 and Swiss-PDBViewer software were used to analyze the conservatism of missense variation sites, whether the variations were harmful and their influences on protein structure and function. MutationTaster and NetGene2 software were used to analyze whether the splice site variation was harmful and its effect on the splice site. Results: The PT and APTT of the proband prolonged to 24.0 s and 69.8 s, respectively. The FⅤ: C and FⅤ: Ag decreased to 6% and 9%, respectively. There were compound heterozygous variations in F5 gene, which included c.911G>A heterozygous missense variation in exon 6 leading to p.Gly276Glu variation and c.5208+1G>A heterozygous missense variation in intron 15. The father and daughter had the p.Gly276Glu heterozygous variation. Her mother and son had the c.5208+1G>A heterozygous variation. Software analysis results of p.Gly276Glu heterozygous variation showed that Gly276 was conserved among homologous species, the variation was harmful, and it could affect the local structure and function of the protein. The c.5208+1G>A heterozygous variation was deleterious and resulted in the disappearance of the splice site, thereby affecting the protein function. Conclusion: The p.Gly276Glu and c.5208+1G>A compound heterozygous variants are deleterious variants associated with the patient's disease and may be the molecular pathogenesis of inherited FⅤ deficiency in this family.目的： 对1个遗传性凝血因子Ⅴ（FⅤ）缺陷症家系进行基因变异分析，探讨其分子发病机制。 方法： 先证者，女，32岁，自幼易鼻出血，通常自愈，2021年3月10日因摔伤致膝盖血肿到空军军医大学第一附属医院就诊。其家系成员均表示无出血等相关病史。采用凝固法检测凝血酶原时间（PT）、活化部分凝血活酶时间（APTT）和凝血因子Ⅴ活性（FⅤ：C）。采用酶联免疫吸附试验（ELISA）检测FⅤ抗原（FⅤ：Ag）。采用Sanger测序法测定F5基因所有外显子及侧翼序列。采用ClustalX-2.1-win、PolyPhen-2及Swiss-PdbViewer软件分析错义变异位点的保守性、是否有害及其对蛋白质结构及功能的影响。采用MutationTaster及NetGene2软件分析剪切变异是否有害及其对剪切位点的影响。 结果： 先证者PT和APTT延长为24.0 s和69.8 s，FⅤ：C和FⅤ：Ag分别降低为6%和9%；其F5基因存在复合杂合变异，分别为6号外显子c.911G>A杂合错义变异，导致p.Gly276Glu变异；15号内含子c.5208+1G>A杂合错义变异。先证者父亲和女儿携带p.Gly276Glu杂合变异；母亲和儿子携带c.5208+1G>A杂合变异。软件分析结果表明，p.Gly276Glu杂合变异的Gly276在同源物种间保守，该变异有害，会影响蛋白局部结构及功能；c.5208+1G>A杂合变异为有害变异，且变异导致剪切位点消失，从而影响蛋白功能。 结论： p.Gly276Glu和c.5208+1G>A复合杂合变异是与患者疾病相关的有害变异，可能是该家系遗传性FⅤ缺陷症的分子发病机制。.