Factor II 20210 G-->A polymorphism associated to factor V Leiden: a report of two thrombophilic families

Impact of the factor II: G20210A variant on the risk of venous thromboembolism in relatives from families with the factor V: R506Q mutation

OBJECTIVES

Factor V: R506Q mutation and the prothrombin G20210A variant (factor II: G20210A variant) are associated with an increased risk of venous thromboembolism (VTE). In cohorts of unrelated patients a cosegregation of both mutations has been shown to be associated with an increased risk of developing VTE. The aim of this study was to investigate the impact of the coinheritance of both mutations on the risk of VTE in relatives of symptomatic carriers of the factor V: R506Q mutation and the factor II: G20210A variant.

PATIENTS AND METHODS

Four families with 48 family members were investigated for the presence of the factor V: R506Q mutation and the factor II: G20210A mutation, and their clinical history was evaluated.

RESULTS

VTE was more frequent in family members with a combined defect (3/10; 30%) compared to those with a single mutation (1/16; 6%) or without a defect (1/12; 8%). The probability for VTE for 40-yr-old individuals with both mutations, a single mutation and no mutation was 56%, 12% and 20%, respectively.

CONCLUSIONS

These data suggest that the G to A transition at position 20210 of the prothrombin gene leads to an increase in the risk of VTE in carriers of the factor V: R506Q mutation. The determination of the factor II: G20210A variant in index patients carrying a factor V: R506Q mutation and, if present, in family members may help to identify individuals who are at high risk for VTE.

High prevalence of thrombophilic genotypes in patients with acute mesenteric vein thrombosis

OBJECTIVES

Mesenteric vein thrombosis is a rare but severe abdominal emergency, often requiring intestinal resection. New genetic prothrombotic defects such as factor V Leiden, the prothrombin transition G20210A, and the methylenetetrahydrofolate reductase TT677 genotype have been described in association with venous thrombosis. Our goal was to assess prevalence and clinical significance of genetic thrombophilia in mesenteric vein thrombosis.

METHODS

Twelve patients with acute mesenteric vein thrombosis were compared with 431 healthy people from the same geographical area. The factor V Leiden, the prothrombin transition G20210A, and the methylenetetrahydrofolate reductase TT677 genotype were identified by polymerase chain reaction and restriction analysis.

RESULTS

A thrombophilic genotype was present in 9 patients (75%): the methylenetetrahydrofolate reductase TT677 genotype was present in 6 (50%), the factor V Leiden in 3 (25%), and the prothrombin transition G20210A in 3 (25%). Combined mutations were present in 4 (33%) patients.

CONCLUSIONS

The factor V Leiden, the prothrombin transition G20210A, and the methylenetetrahydrofolate reductase TT677 genotype are important predisposing factors in the pathogenesis of mesenteric vein thrombosis. Their identification bears strong clinical implications for management of patients with mesenteric vein thrombosis.

Combinations of 4 mutations (FV R506Q, FV H1299R, FV Y1702C, PT 20210G/A) affecting the prothrombinase complex in a thrombophilic family

The study of the molecular bases of thrombophilia in a large family with 4 symptomatic members is reported. Three thrombophilic genetic components (FV R506Q, FV H1299R, and PT 20210G/A), all affecting the activity of the prothrombinase complex, were detected alone and in combination in various family members. In addition, a newly identified missense mutation (factor V [FV] Y1702C), causing FV deficiency, was also present in the family and appeared to enhance activated protein C (APC) resistance in carriers of FV R506Q or FV H1299R by abolishing the expression of the counterpart FV allele. The relationships between complex genotypes, coagulation laboratory findings, and clinical phenotypes were analyzed in the family. All symptomatic family members were carriers of combined defects and showed APC resistance and elevated F1 + 2 values. Evidence for the causative role of the FV Y1702C mutation, which affects a residue absolutely conserved in all 3 A domains of FV, factor VIII, and ceruloplasmin, relies on (1) the absolute cosegregation between the mutation and FV deficiency, both in the family and in the general population; (2) FV antigen and immunoblot studies indicating the absence of Y1702C FV molecules in plasma of carriers of the mutation, despite normal levels of the FV Y1702C messenger RNA; and (3) molecular modeling data that support a crucial role of the mutated residue in the A domain structure. These findings help to interpret the variable penetrance of thrombosis in thrombophilic families and to define the molecular bases of FV deficiency.

Combinations of 4 mutations (FV R506Q, FV H1299R, FV Y1702C, PT 20210G/A) affecting the prothrombinase complex in a thrombophilic family

The study of the molecular bases of thrombophilia in a large family with 4 symptomatic members is reported. Three thrombophilic genetic components (FV R506Q, FV H1299R, and PT 20210G/A), all affecting the activity of the prothrombinase complex, were detected alone and in combination in various family members. In addition, a newly identified missense mutation (factor V [FV] Y1702C), causing FV deficiency, was also present in the family and appeared to enhance activated protein C (APC) resistance in carriers of FV R506Q or FV H1299R by abolishing the expression of the counterpart FV allele. The relationships between complex genotypes, coagulation laboratory findings, and clinical phenotypes were analyzed in the family. All symptomatic family members were carriers of combined defects and showed APC resistance and elevated F1 + 2 values. Evidence for the causative role of the FV Y1702C mutation, which affects a residue absolutely conserved in all 3 A domains of FV, factor VIII, and ceruloplasmin, relies on (1) the absolute cosegregation between the mutation and FV deficiency, both in the family and in the general population; (2) FV antigen and immunoblot studies indicating the absence of Y1702C FV molecules in plasma of carriers of the mutation, despite normal levels of the FV Y1702C messenger RNA; and (3) molecular modeling data that support a crucial role of the mutated residue in the A domain structure. These findings help to interpret the variable penetrance of thrombosis in thrombophilic families and to define the molecular bases of FV deficiency.

Inherited coagulation disorders in cirrhotic patients with portal vein thrombosis

The prevalence and pathogenesis of portal vein thrombosis (PVT) in patients with cirrhosis without hepatocellular carcinoma are not clearly defined. The role of thrombophilic genetic factors is well established in other venous thrombotic diseases, as well as in noncirrhotic portal thrombosis. Recently, new, inherited thrombophilic disorders (factor V Leiden [FVL], mutation G20210A of prothrombin [PTHR A(20210)], and mutation TT677 of methylenetetrahydrofolate reductase [MTHFR C677-->T]) have been identified and associated with increased risk of venous thrombosis. The aim of our study was to investigate the role of these thrombophilic disorders in the pathogenesis of PVT in cirrhotic patients. Twenty-three cirrhotic patients with PVT and 40 cirrhotics without PVT were included. A group of 184 patients with deep vein thrombosis (DVT) and 431 healthy persons served as controls. The FVL, PTHR A(20210), and MTHFR C(677)-->T genotypes were identified by a polymerase chain reaction and restriction analysis. The frequencies of FVL, PTHR A(20210) mutation, and homozygous MTHFR C(677)-->T were 13%, 34.8%, and 43.5% in cirrhotic patients with PVT and 7.5%, 2.5%, and 5% in cirrhotic patients without PVT, respectively. Five patients in the former group had associated defects. A thrombophilic genotype was detected in 69.5% of the patients with PVT. Identification of this high-risk group may have implications in patients who are candidates for major surgery or liver transplantation, and may influence the duration of oral anticoagulation.