Molecular and clinical characterization of two unrelated families with factor V deficiency, including a novel nonsense variant (p.Gln1532*)

Background

Factor V (FV) is an essential cofactor in the coagulation cascade. The characterization of novel mutations is advantageous for the clinical management of FV-deficient patients.

Methods

Coagulation screening and thrombin generation assay were performed with the plate-poor plasma. All 25 exons of the F5 gene were amplified and sequenced. The ClustalX-2.1 software was applied to the multiple sequence alignment. The possible adverse effects of mutations were investigated with online bioinformatics software and protein modeling.

Results

Two unrelated families with FV deficiency were under investigation. Proband A was an 18-year-old youth with recurrent epistaxis. Proband B was a 29-year-old woman who did not present with any bleeding symptoms. Three heterozygous mutations (p.Gln1532*, p.Phe218Ser, and p.Asp2222Gly) were detected. Interestingly, they were compound heterozygotes and both contained the p.Asp2222Gly, a polymorphism. The thrombin generation assay showed that both patients had impaired ability of thrombin generation, and in particular, proband A was more severe. Conservation, pathogenicity and protein modeling studies all indicated that these three mutations could cause deleterious effects on the function and structure of FV.

Conclusion

These three mutations are responsible for the FV-deficient in two pedigrees. Moreover, the nonsense variant p.Gln1532* is first reported in the world.