Risk Of Thrombosis In Carriers Research Articles

Coexistence of hypofibrinogenemia and factor V Leiden mutation

Congenital hypofibrinogenemia and afibrinogenemia are usually associated with an increased risk of bleeding, but occurrence of arterial or venous thrombosis has also been reported in individuals with fibrinogen deficiency. This study reports on a 25-year-old patient with hypofibrinogenemia (fibrinogen 0.6 g/l) and congenital thrombophilia due to heterozygous factor V Leiden mutation who developed spontaneous deep-vein thrombosis (DVT) in the right lower extremity. Regardless of hypofibrinogenemia, he was receiving anticoagulant therapy over 6 months, with no occurrence of bleeding. His father is also a heterozygous carrier of factor V Leiden, but with normal fibrinogen level and he remained asymptomatic despite having experienced surgery in the past. This case, as well as data from literature, suggests that risk of thrombosis in carriers of factor V Leiden mutation is not counterbalanced by moderate congenital hypofibrinogenemia, and that antithrombotic prophylaxis should not be omitted in high-risk situations for occurrence of thrombosis in patients with coinheritance of hypofibrinogenemia and factor V Leiden mutation.

Role of the C‐sheet in the maturation of N‐glycans on antithrombin: functional relevance of pleiotropic mutations

The characterization of natural mutants identified in patients with antithrombin deficiency has helped to identify functional domains or regions of this key anticoagulant and the mechanisms involved in the deficiency, as well as to define the clinical prognosis. Recently, we described an abnormal glycosylation in a pleiotropic mutant (K241E) that explained the impaired heparin affinity and the mild risk of thrombosis in carriers. To evaluate the effects of different natural pleiotropic mutations on the glycosylation of antithrombin and their functional effects. Five pleiotropic mutations identified in patients with antithrombin deficiency and located at each one of the strands of the C-sheet were selected (K241E, M251I, M315K, F402L, and P429L). Recombinant mutants were generated and purified. Glycoform heterogeneity and conformational sensitivity were studied with electrophoresis, proteomic analysis, and glycomic analysis. Heparin affinity was evaluated from intrinsic fluorescence. Reactivity assays with factorXa, thrombin and neutrophil elastase in the presence or absence of heparin were also performed. Pleiotropic mutants, except for that with the M315K mutation, which affects a non-exposed residue, showed two glycoforms. Variant1, with abnormal glycosylation, had reduced heparin affinity and severely affected reactivity with the target proteases. In contrast, variant2, with similar electrophoretic mobility and heparin affinity to wild-type antithrombin, had impaired inhibitory activity that was partially compensated for by activation with heparin. Our results suggest the C-sheet of antithrombin as a new region that is relevant for proper maturation of the N-glycans. Therefore, pleiotropic mutations lead to glycosylation defects that are responsible for the reduced heparin affinity.

Association of C46T genetic polymorphism of coagulation factor XII with deep venous thrombosis: a cohort study on Egyptian patients

Deep vein thrombosis (DVT) is a common multi-factorial disease, with serious short- and long-term complications, and a potential fatal outcome. Many genes are involved in determining the interindividual variation in traits that define the onset and progression of disease, as well as the response to treatment. Several association studies have designed the relationship between factor XII C46T polymorphism and the risk of arterial and venous thrombosis. Some studies reported that FXII gene polymorphism is not associated with venous thrombosis, whereas other studies found an increased risk of venous thrombosis in carriers of a FXII-T variant. We constructed an age–gender–ethnic–matched case–control study including 52 DVT patients and 100 healthy volunteers. C46T polymorphism of the coagulation factor XII was carried out using allelic discrimination assay by real-time polymerase chain reaction for patients and controls, while plasma factor XII activity was detected by one-step clotting assay. FXII C46T genotyping in DVT patients revealed that 34.6% were heterozygous harboring the FXII-CT heterotype and 3.85% were homozygous; FXII-TT homotype, with no statistically significant difference in the distribution of the mutant genotypes between DVT patients and the control group. FXII activity was significantly reduced in DVT patients harboring the mutant genotypes. In the present study, FXII C46T gene polymorphism was not associated with increased risk of deep venous thrombosis.

Variable plasma levels of Factor V Leiden correlate with circulating platelet microparticles in carriers of Factor V Leiden

Introduction Inheritance of Factor V Leiden (FVL) is associated with an increased but variable level of risk for thrombosis. We have previously shown that FVL heterozygotes have elevated levels of circulating pro-coagulant microparticles (MP). Here we sought to determine if these subjects differed in their plasma levels of FVL and if this was related to MP concentrations and/or history of thrombosis. Materials and Methods The Hemoclot Quanti. V-L clotting assay was used to specifically measure FVL in plasma samples from 44 known carriers (12 M, 32 F; aged 46 ± 13 years). Circulating MP were quantified by flow cytometry using fluorochrome conjugated antibodies to platelet (CD41a), leukocyte (CD45), and endothelial (CD62e) surface markers, and MP prothrombinase activity was determined by ELISA. Results The cohort was found to have a mean FVL of 49.5 ± 5.6% and this was positively correlated to the total number of circulating CD41a + MP (R = 0.31, p = 0.03) but not to other MP subsets or to MP prothrombinase activity. The amount of FVL relative to normal factor V (FVL/FV clotting ratio) was calculated and found to be highly variable, ranging from 0.37 to 0.69, and significantly correlated with a history of thrombosis (n = 14; p = 0.04). Conclusions This is the first study to investigate the relationship between varying levels of FVL and plasma derived MP. These results are consistent with our previous findings of an increase in MP levels in carriers of FVL as compared to controls, and suggest a role for FVL/FV ratio in predicting risk of thrombosis in carriers of FVL.

Cerebral venous sinus thrombosis as a recurrent thrombotic event in a patient with heterozygous prothrombin G20210A genotype after discontinuation of oral anticoagulation therapy: How long should we treat these patients with warfarin?

Cerebral venous sinus thrombosis is an uncommon condition with many clinical manifestations, and hereditary prothrombotic conditions such as factor Leiden V, deficiency of protein S, protein C and antithrombin III, as well as prothrombin gene mutation, may account for 10-15% of cases. To date, conflicting results have been reported for recurrent venous thrombosis in the patients with factor V Leiden and prothrombin G20210A mutation, since some studies have shown a higher risk for recurrent venous thrombosis in carriers of these two mutations than in non-carriers, and the last study showed higher risk only for carriers of double defect (homozygous or double heterozygous for this mutations). Case report is presented. We report a case of cerebral sinus thrombosis as a recurrent thrombotic event in a patient with heterozygous prothrombin G20210A genotype after discontinuation of oral anticoagulation therapy. Since many facts are controversial, the use of secondary prophylaxis for thrombosis in these patients is still a matter of debate without clear consensus recommendation. Data on the risk of recurrent thrombotic events in thrombophilic patient is insufficient. The main unclear question concerning these patients is: how long and whom should we treat with long-term anticoagulant therapy as secondary prophylaxis of DVT? The problem for practitioner is that we do not have guidelines and precise recommendations for secondary thromboprophylaxis in this or similar cases. This case is remarkable for its favorable and quick outcome and its rarity, because CSVT is an uncommon condition and heterozygous prothrombin G20210A genotype was only found predisposing factor for CSVT. Further studies of risk of recurrent venous thrombosis in patients with heterozygous prothrombin G20210A genotype with the larger sample size are required.

Soluble endothelial protein C receptor (sEPCR) levels and venous thromboembolism in carriers of two dysfunctional protein C variants

The role of the A3 haplotype and soluble endothelial protein C receptor (sEPCR) plasma levels in predisposing the carriers of two peculiar dysfunctional protein C (PC) variants (PC Arg-1→Cys and PC Arg-1→Leu, also known as PC Padua 2 and PC Padua 3, respectively) to venous thromboembolism (VTE) has been evaluated. The levels of sEPCR have been assessed in family members during 6 years of follow-up and correlated to the presence of the A3 haplotype. Individuals who carried both a dysfunctional PC and the A3 haplotype and presenting with high levels of sEPCR experienced severe VTE at young age. The increased plasma levels of sEPCR were not related to excessive thrombin generation. Carriers of the A3 haplotype showed levels of sEPCR above 135 ng/ml (80th percentile of the distribution in healthy subjects), which remained elevated during the follow-up. In non-carriers of the A3 haplotype, sEPCR levels remained persistently around 100 ng/ml or lower. In conclusion, we have observed that elevated sEPCR plasma levels and the concomitant presence of the A3 haplotype of EPCR gene are associated with severe thrombotic manifestations in carriers of two dysfunctional PC variants. Whether high plasma levels of sEPCR and/or the presence of the A3 haplotype increase the risk of thrombosis in carriers of other PC defects or thrombophilic conditions remains to be clarified.

Influence of the 4600A/G and 4678G/C polymorphisms in the endothelial protein C receptor (EPCR) gene on the risk of venous thromboembolism in carriers of factor V Leiden

Two polymorphisms in the endothelial protein C receptor (EPCR) gene, 4600A/G and 4678G/C, have been reported to influence the risk of venous thromboembolism (VTE). The objective of this study was to assess whether these polymorphisms modify the risk of VTE in carriers of factor V (FV) Leiden. We genotyped 295 carriers of FV Leiden for these polymorphisms: 100 unrelated patients with a history of VTE (propositi) and 195 relatives (14 of them symptomatic) of 81 of the propositi. Spontaneous VTE events occurred in 71% of propositi carrying the 4678GG genotype, 65% carrying the GC, and 43% with the CC genotype. The mean age at the first onset was significantly higher in propositi carrying the 4678CC than in those with the GC or GG genotype (p = 0.046). Among the 276 carriers of FV Leiden from the 81 families studied, the 95 symptomatic members had similar 4600G allele and 4600AG genotype frequencies but significantly lower 4678C allele (p = 0.002) and 4678CC genotype (p = 0.004) frequencies than the 181 asymptomatic members. The probability of being free of thrombosis at age 40 was significantly higher in the 66 carriers of the 4678CC genotype (94%) than in the 138 carrying the GC (72%) or in the 72 with the 4678GG genotype (60%) (p < 0.001). Multivariate analysis showed that the 4678CC genotype reduced the risk of thrombosis in carriers of FV Leiden (OR = 0.31;95% CI = 0.16-0.83). The incidence of VTE was higher in the 195 relatives with FV Leiden than in the 133 without FV Leiden (OR = 4.7; CI = 1.3-7.2). These results show that carriers of FV Leiden with the 4678CC genotype have a significantly reduced risk of VTE compared with those carrying the 4678GG or GC genotype, probably due to the higherAPC levels previously observed in individuals carrying the 4678CC genotype.

Thrombophilic predisposition in stroke and venous thromboembolism in Danish patients.

The present study describes 403 patients with thrombosis, from a uniform ethnic and geographical background. Two-hundred-and-seven individuals had suffered mild or moderate stroke and 196 individuals suffered venous thromboembolism. We recorded levels of antithrombin, protein C and protein S, plasminogen and plasma homocysteine, and the presence of the factor V Leiden mutation, the prothrombin 20210G-->A variant, and the methylenetetrahydrofolate reductase (MTHFR) 677C-->T polymorphism. Controls for the mutation frequencies consisted of Guthrie card blood spots from a cohort of new-born babies. The cumulative prevalence of deficiencies in antithrombin, protein C, protein S or plasminogen was 2.4% in patients with stroke and 11.2% in patients with venous thrombosis. The factor V Leiden mutation was present in 11.1% of patients with stroke and 26.5% of patients with venous thrombosis, compared with 6.6% of controls (n = 4188; P < 0.05 and P < 0.0001, respectively). The prevalence of the prothrombin 20210A variant was 3.1% in patients with venous thrombosis, 1.9% in patients with stroke and 2.0% in controls (n = 500; P > 0.05). Hyperhomocysteinemia was present in 16.0% of patients with stroke and 17.6% of patients with venous thrombosis. The prevalence of the MTHFR 677T/T genotype was no different in patients with stroke (10.6%) and venous thrombosis (8.7%) than in controls (8.3%; n = 1084; P > 0.05); thus, it apparently contributed to thrombosis only via its influence on total plasma homocysteine, which was significantly increased in patients with the T/T genotype (P < 0.001). The MTHFR T/T genotype did not further increase the risk for thrombosis in carriers of the factor V Leiden mutation. Overall, thrombotic events were associated with a known risk factor in 27% of patients with stroke and 55% of patients with venous thrombosis.

Incidence of Venous Thromboembolism in Families with Inherited Thrombophilia

The risk of spontaneous or risk-period related venous thromboembolism in family members of symptomatic carriers of antithrombin (AT), protein C (PC) or protein S (PS) defects, as well as of the Factor V Leiden mutation is still undefined. We performed a retrospective cohort study in family members (n = 793) of unselected patients with a documented venous thromboembolism and one of these deficiencies to make an estimate of this risk. The annual incidences of total and spontaneous venous thromboembolic events in carriers of AT, PC or PS defects (n = 181) were 1.01% and 0.40%, respectively, as compared to 0.10% and 0.04% in non-carriers, respectively (relative risks both 10.6). In carriers of Factor V Leiden (n = 224), the annual incidences of total and spontaneous venous thromboembolism were 0.28% and 0.11%, respectively, as compared to 0.09% and 0.04% in non-carriers, respectively (relative risks 2.8 and 2.5). Additional risk factors (immobilisation, surgery and trauma: oral contraceptive use; and pregnancy/ post-partum) increased the risk of thrombosis in carriers of AT, PC and PS defects as compared to non-carriers (relative risks 8.3, 6.4 and 8.2, respectively). Oral contraceptive use and pregnancy/ post-partum period increased the risk of thrombosis in carriers of Factor V Leiden to 3.3-fold and 4.2-fold, respectively, whereas other risk factors had only a minor effect. These data lend some support to the practice of screening family members of symptomatic carriers of a AT, PC and PS deficiency. For family members of symptomatic carriers of Factor V Leiden, screening does not seem to be justified except for women in fertile age.

The prothrombin 20210 G to A variation and thrombosis.

The 20210 G to A variation in the prothrombin gene was first described in 1996 and found to be associated with both elevated plasma prothrombin levels and a moderately increased risk for first venous thrombotic events. These findings generally have been confirmed in several independent studies. The 20210A allele seems to be rather common in white subpopulations, among whom the prevalence of heterozygous carriers may vary from 1% to 5%. The variant prothrombin allele contributes to the risk of thrombosis in carriers of other genetic risk factors (eg, factor V Leiden); also, this allele seems not to be an important risk factor for arterial thrombosis, unless risk factors for cardiovascular disease (eg, smoking) also are present.

Increased risk of venous thrombosis in carriers of natural anticoagulant deficiencies. Results of the family studies of the Spanish Multicenter Study on Thrombophilia (EMET study).

Several studies have demonstrated a higher risk of thrombosis in carriers of anticoagulant deficiencies than in non-deficient individuals from families with thrombophilia. The prevalences in Spain were established in a multicenter study (the EMET study) and all the deficient individuals were invited to recruit all available family members to be screened for the same deficiency in order to establish the risk of thrombosis in deficient individuals. Five-hundred-and-eighty-three individuals from 114 families with natural anticoagulant deficiencies were analysed. Propositi and relatives with a history of thrombosis were asked about the localization and the age at the first episode and whether or not it was spontaneous. Three families with antithrombin deficiency, 35 with protein C, 60 with protein S, four with plasminogen, four with heparin cofactor II, seven with combined deficiencies and one family with dysfibrinogenemia were included in the analysis. The risk of thrombosis was increased for individuals deficient in antithrombin (adjusted odds ratio 21.23; 95% confidence interval 5.71-78.94), protein C (adjusted odds ratio 12.62; 95% confidence interval 4.75-33.51), protein S type I (adjusted odds ratio 19.95; 95% confidence interval 7.40-53.82), protein S type III (adjusted odds ratio 8.11; 95% confidence interval 2.66-21.99) or in protein C plus protein S (adjusted odds ratio 8.99; 95% confidence interval 2.79-28.93), but not for those deficient in plasminogen or heparin cofactor II. The thrombosis-free survival was shortened for deficient individuals in antithrombin (median 30 years), protein C (median 46 years), protein S type-I (median 48 years), protein S type III (median 61 years) and combined protein C and S (median 40 years). In conclusion, individuals carrying anticoagulant deficiencies have an increased risk of thrombosis, especially those with antithrombin, protein C or type I protein S deficiencies.