A Case Control Study of Deep Venous Thrombosis in Relation to Factor V G1691A (Leiden) and A4070G (HR2 Haplotype) Polymorphisms.

Activated protein C resistance (APCR) is a significant risk factor for venous thromboembolism (VTE), and the factor V (FV) gene mutations G1691A (FV-Leiden) account for the majority of inherited APCR cases. An additional FV gene mutation, the A4074G (FV-HR2), was recently reported to induce a risk of VTE by some but not all groups. The aim of this study was to determine the prevalence of single and combined SNPs in 126 patients with documented deep venous thrombosis (DVT), and 197 control Tunisian subjects. The frequencies of FV-Leiden A allele (p <0.001; OR = 5.031), and HR2 G allele (p = 0.014; OR = 2.463) were significantly higher among DVT patients. Genotype differences were found between FV-Leiden G/A (p <0.001; OR = 3.936) and A/A (p = 0.013; OR = 11.529), but not HR2 A/G genotypes (p = 0.862; OR = 1.166), between patients and controls. While no linkage disequilibrium was noted between the FV 1691A and 4070G or A alleles, higher prevalence of the 1691G/4070G (p = 0.002; OR = 5.189) and the 1691A/4070A (p = 0.007; OR = 3.670) were noted among DVT patients than in control subjects. Collectively, this indicates that FV-Leiden, and to a lower extent HR2 haplotype, are important independent risk factors for DVT, and that their coinheritance does not increase significantly the DVT risk imparted by either.