Genetic Analysis of a Family With Hereditary Factor V Deficiency Induced by Compound Heterozygous Variants (IVS24+3A>T and p.Asp2222Gly)

OBJECTIVE: Factor V(FV) is a critical cofactor in the coagulation cascade. The diagnosis and investigation of novel variant contribute to improving the clinical treatment and management of patient with Factor V deficiency. METHODS: Coagulation screening, FV activity, FV antigen levels and thrombin generation assay (TGA) were performed on plateletpoor plasma samples collected from eleven family members. All exons and flanks of F5 gene were analysed by Sanger sequencing and novel variant were confirmed by reverse sequencing. Online bioinformatics tools were used to investigate possible adverse and effects on splicing of proband's F5 gene novel variant. Thromboelastography (TEG) and TGA were utilized to detect and evaluate the coagulation function of proband and heterozygous carrier family members. RESULTS: The proband was a middle-aged Chinese woman with menorrhagia, presenting as an FV deficiency patient with FV activity and antigen levels of 7% (reference: 86%-114%) and 6% (reference: 70%-140%), respectively. Genetic testing revealed that proband carried compound heterozygous variants in F5 gene: c.6528+3A>T(IVS24+3A>T) and c.6665A>G(p.Asp2222Gly). Multiple online tools indicate that the novel variant represents a genuine splice-site, leading to the deletion of a fragment and triggering exon skipping. The TGA results indicate decreased thrombin generation capacity in the proband, while TEG showed prolonged clotting initiation time. CONCLUSION: The proband with hereditary factor V deficiency carries compound heterozygous variants, IVS24+3A>T and p.Asp2222Gly, which have led to alterations in clinical phenotype, genotype, and function. The IVS24+3A>T variant in the F5 gene is a novel splice-site variant reported here for the first time.