The incidence of venous thromboembolism in carriers of antithrombin, protein C or protein S deficiency associated with the HR2 haplotype of factor V: a family cohort study

In order to assess whether the HR2 haplotype of the factor V gene (HR2) increases the risk of venous thromboembolism (VTE) in carriers of antithrombin (AT), protein C (PC) or S (PS) defects, we performed this determination in 336 subjects, who were family members of 66 symptomatic patients with clotting inhibitors defects. We first assessed the presence of previous VTE, and then followed prospectively subjects without prior VTE. VTE episodes had occurred in 26 individuals: 18 in 139 carriers of clotting inhibitors defects alone (annual incidence, 0.55%), four in 33 carriers of clotting inhibitors defects combined with HR2 (0.52%) and four in 151 non-carriers (0.1%), resulting in a relative risk (RR) for VTE of 4.9 (95% CI: 1.7-14.4) and 4.62 (95% CI: 1.2-18.4), respectively. After an overall follow-up of 2557 patient-years, VTE episodes developed in 12 subjects: nine in 121 carriers of clotting inhibitors defects alone (annual incidence, 0.92%), three in 29 carriers of clotting inhibitors defects combined with HR2 (1.0%) and none in 147 non-carriers. In family members of patients with AT, PC or PS defects the coinheritance of HR2 haplotype does not seem to increase the thromboembolic risk.

Recurrent venous thrombosis with factor V Leiden mutation

A patient who presented with recurrent venous thrombosis is reported. Following an episode of spontaneous deep vein thrombosis of the lower limb he was started on oral anticoagulant therapy, which he discontinued. He presented with cerebral venous thrombosis and improved partially with anticoagulant therapy. Evaluation for hypercoagulable states revealed factor V Leiden mutation by polymerized chain reaction method. Long-term anticoagulation has been planned. Evaluation for factor V Leiden mutation is always warranted in patients presenting with spontaneous thrombosis, especially if there is recurrent thrombosis.

Causes of portal venous thrombosis in cirrhotic patients: the role of genetic and acquired factors

OBJECTIVE AND METHODS

We compared frequencies of three common prothrombotic mutations (factor V Leiden, the G20210A mutation of the prothrombin gene, and homozygosity for C677T methylenetetrahydrofolate reductase) in 219 cirrhotic patients, 43 with and 176 without portal vein thrombosis (PVT). The following variables were related to PVT: prothrombin levels, platelet count, Child-Pugh classification, previous abdominal surgery, number of decompensation events, size of varices, red markers on varices, and sclerotherapy. All patients were followed up for a mean period of 18 months (range 10-30).

RESULTS

Prothrombotic mutations were detected in 64 of the 219 cirrhotic patients (29.2%), at equal frequency in patients with or without PVT. At univariate analysis, PVT was associated with Child-Pugh classes B and C, signs of liver decompensation, large varices with red markings, sclerotherapy, and abdominal surgery. At multivariate analysis, PVT was associated with sclerotherapy [odds ratio (OR) 4.9, 95% confidence interval (CI) 2.2-11] and previous surgery (OR 2.8, 95% CI 1.2-6.3). The combination of the two acquired factors increased the risk of PVT, whereas the combination of local with genetic defects did not. Only a single patient with genetic thrombophilia and without PVT at inclusion developed the complication during follow-up, concomitantly with the development of hepatocellular carcinoma.

CONCLUSION

In cirrhotic patients prothrombotic mutations by themselves are not causative of PVT. Sclerotherapy and previous abdominal surgery favour the development of two-thirds of cases of PVT; in the remaining cases the pathogenesis remains elusive.

HR2 haplotype in Arab population and patients with venous thrombosis in Kuwait

BACKGROUND

Venous thromboembolism (VTE) occurs due to a number of hereditary and acquired disorders of hemostasis. A recently identified polymorphism in factor V gene (A4070G; named HR2) has been reported to be a possible risk factor for the development of VTE, with a high prevalence of 9.5%-15.2% in patients of different ethnic groups in different parts of the world. However, the prevalence of HR2 has not yet been tested in VTE patients of Arab ethnicity.

OBJECTIVES

To study the prevalence and possible risk of HR2 haplotype in Arabs.

PATIENTS/METHODS

Exactly 188 VTE patients and 100 healthy subjects, all being of Arab ethnicity, were examined for HR2 using Polymerase chain reaction, restriction fragment length polymorphism and agarose gel electrophoresis.

RESULTS

Data showed that 31 patients and seven healthy subjects had HR2 haplotype, with a prevalence of 16.5% and 7%, respectively. Furthermore, 43 patients (22.9%) had more than one risk factor for VTE.

CONCLUSIONS

The prevalence of HR2 in Arabs is quite high, with a 2.62-fold greater risk of developing VTE. Moreover, coexistence of two or more genetic/acquired defects of VTE is quite common in Arab patients.

Venous thrombosis in inflammatory bowel disease

Patients with inflammatory bowel disease (IBD) have a threefold increased risk of venous thrombosis, a major cause of morbidity and mortality. Although the exact mechanism explaining the initiation of thrombosis remains unclear, it is likely to be a multifactorial process. Reported abnormalities include activation of markers of the coagulation cascade, disturbed fibrinolysis and the activation of platelets. The contribution of thrombophilic disorders such as factor V Leiden, prothrombin gene mutations and hyperhomocysteinaemia are discussed, but their role in thrombosis associated with IBD has remained unclear. Recent research has examined elevated CD40, P-selectin levels and tissue factor-bearing microvesicles in venous thrombosis, and the relevance of these observations to IBD is reviewed.

[Pharmacogenetics of the local thrombolysis in patients with deep vein thrombosis]

Thrombophilia, the state of increased tendency for blood clotting, is considered the disorder of a complex etiology, caused by both environmental and genetic factors. As gene variants predisposing to thrombophilia and influencing the increased risk of vein thrombosis might influence response to local thrombolysis, the aim of the work was to characterize the pharmacogenetic conditions for local streptokinase treatment in patients with a deep vein thrombosis (DVT) of lower extremities based on the following polymorphism analyses: G1691A polymorphism of factor V (FV), G20210A polymorphism of prothrombin (PT), A4250G (Thr312Ala) polymorphism of fibrinogen-alpha (FGA), G(-455)A polymorphism of fibrinogen-beta (FGB), 4G/5G polymorphism of plasminogen activator inhibitor type 1(PAI-1) and insertion/deletion (I/D) polymorphism of tissue plasminogen activator (t-PA). The study included 40 DVT patients who underwent a local thrombolytic treatment within 14-day period from diagnosis. Full recanalization was achieved in 20 subjects (50%) [group R(+)], whereas incomplete or total lack of recanalization was identified in the remaining 20 patients [group R(-)]. No major complications of thrombolytic treatment occurred in the studied group. In the case of prothrombin gene all individuals carried homozygous wild type genotype (GG). Prevalence of the genotypes and alleles of the remaining five polymorphisms did not differ significantly between the groups R(+) and R(-). Neither sex nor age, smoking or time period from diagnosis to introduction of the thrombolytic treatment significantly influenced treatment efficacy. The results of the study suggest that a local thrombolysis with streptokinase introduced within two week period from the diagnosis is a safe and efficient method of treatment for deep vein thrombosis of lower extremities. However, size of the group is insufficient to clearly determine the association between investigated polymorphisms and efficacy of local treatment with streptokinase.

Portal vein thrombosis: what is the role of genetics?

The aetiology of portal vein thrombosis (PVT) in adults is complex. Risk factors include local precipitating factors and acquired and inherited factors, an area in which there has been much recent progress. Although PVT in the absence of cirrhosis may be regarded as a somewhat different disorder to PVT in the presence of cirrhosis, in both cases most studies support a role of the prothrombin G20210A mutation. Some differences in risk factors observed between different studies may relate partly to referral patterns or study design, although individual patients may develop PVT as a result of differing combinations of risk factors. The demonstration of an inherited thrombophilic mutation in a subset of PVT may ultimately inform clinical management regarding the use and duration of anticoagulation therapy, although there is a need for evidence from randomized-controlled clinical trial data.

Management options for thrombophilias

Thrombophilias may be inherited or acquired, continuing or transient, and may contribute strongly or weakly to thrombosis. They may predispose to venous thromboembolism alone or also to artery occlusion. Advice on management must recognize these variations. The presence of an inherited thrombophilia should not alter the intensity of anticoagulant therapy, given that antithrombin, protein C, or protein S deficiency, factor V Leiden, and the prothrombin G20210A mutation are not unusually anticoagulant resistant. However, they can increase the optimal treatment duration after a first thromboembolic event. Optimal duration depends on the balance between thrombosis risk off treatment and bleeding risk during extended anticoagulant therapy, and needs to be separately estimated for each individual with thrombosis and thrombophilia. The higher the thrombosis risk and the lower the bleeding risk, the longer the optimal treatment duration. This balance favors continued (but perhaps not indefinite) therapy in antithrombin, protein C, and protein S deficiency, and perhaps also in patients with the factor V Leiden or prothrombin mutations if their bleeding risk is low. Thrombosis that complicates active malignancy, the antiphospholipid syndrome, or heparin-induced thrombocytopenia needs special consideration: recent clinical trials suggest that low molecular weight heparins are more effective than warfarin in thrombosis with cancer, and that a more intense warfarin effect is not needed for patients with antiphospholipid syndrome and thrombosis. Debate continues about the place of screening for presymptomatic but affected relatives of patients with thrombosis and an inherited predisposition. It is essential that any family testing be done only with the informed consent of all concerned. Given consent, there is general support for family testing in antithrombin, protein C, or protein S deficiency and where the factor V Leiden or prothrombin mutation is strongly penetrant and expressed. There is, however, a strong argument that any testing in families in which clotting factor polymorphisms are weakly expressed should be restricted to young women when they consider hormonal contraception or pregnancy, given that these acquired factors multiply the risk.

Risk factors for venous thrombosis in Swedish children and adolescents

AIM

To identify prothrombotic risk profiles in children and adolescents referred to a regional coagulation centre in southern Sweden for a first thrombotic event.

METHODS

One hundred and twenty-eight consecutive children and adolescents (newborn to 20 y) referred for evaluations of a first episode of venous thrombosis were investigated. Clinical data were collected retrospectively, and the following variables were investigated: protein C, protein S, antithrombin; resistance to activated protein C; the genotypes FV-G1691A, F II-G20210A, MTHFR-C677T, MTHFR- A1298C; coagulation factors VIII and XI.

RESULTS

104/128 subjects (81%) had identifiable acquired risk factors, most often indwelling catheters and hormone therapy. Predisposing genetic factors related to thromboembolic events were revealed in 53/83 (64%) of subjects who agreed to follow-up blood sampling, and 17/83 (20%) had two or more inherited risk factors. Combinations of genetic and acquired risk factors were identified in 45/83 (54%) of the subjects, and 77/83 (93%) had at least one such risk factor. Both sexes had one peak in frequency at less than 1 y of age and then an increase during adolescence, more in females than in males. Plasma values for coagulation factors VIII and XI were age appropriate and showed a normal Gaussian distribution.

CONCLUSION

This study identified prothrombotic risk profiles in almost all children and adolescents with venous thrombosis, which underlines the importance of careful evaluation of genetic and acquired risk factors.

A Case Control Study on the Contribution of Factor V-Leiden, Prothrombin G20210A, and MTHFR C677T Mutations to the Genetic Susceptibility of Deep Venous Thrombosis

BACKGROUND

Insofar as the inherited prothrombotic single nucleotide polymorphisms (SNPs) factor V G1691A (FV-Leiden), prothrombin (PRT) G20210A, and methylenetetrahydrofolate reductase (MTHFR), C677T are inherited risk factors of venous thromboembolism (VTE), the aim of this study was to determine the prevalence of single and combined SNPs in 198 patients with documented deep venous thrombosis (DVT), and 697 control subjects, and to estimate the associated risks.

METHODS

Factor V-Leiden, PRT G20210A, and MTHFR C677T were analyzed by PCR and restriction fragment length polymorphism (RFLP).

RESULTS

The prevalence of the heterozygote and homozygous variants for FV-Leiden (52.02 vs. 14.78%, RR 6.28), PRT G20210A (19.2 vs. 3.6%; RR 6.38), and to a lesser extent the T/T genotype of MTHFR C677T (20.71 vs. 11.0%; RR 1.49) were higher among DVT patients vs. controls, respectively. Two or more SNPs were detected in 90 of 198 patients (45.5%) and in 60 of 697 controls (8.6%), with odds ratios of 16.754 for joint occurrence of FV-Leiden and PRT G20210A, 10.471 for FV-Leiden and MTHFR C677T, and 6.283 for PRT G20210A SNPs and MTHFR 677T/T. Logistic regression analysis showed a further increased odds for FV-Leiden in combination with PRT G20210A (85.198) or homozygous MTHFR C677T (81.133), and to a lesser extent for PRT G20210A in combination with homozygous MTHFR C677T (20.812).

CONCLUSIONS

This indicates that FV-Leiden and PRT G20210A, more than MTHFR C677T, are important risk factors for DVT, and that the presence of more than one prothrombotic SNPs was associated with a significant risk of DVT.

Multiplex PCR-RFLP assay for detection of factor V Leiden and prothrombin G20210A

Factor V Leiden and prothrombin G20210A are clinically relevant genetic risk factors for venous thrombosis. Molecular diagnostic testing for factor V Leiden and prothrombin G20210A is widespread, and laboratories use a variety of technical approaches. Here we introduce a multiplex polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) based on single (Mn/l) restriction endonuclease digestion. The assay was shown to simultaneously and accurately detect factor V Leiden and prothrombin G20210A mutations.

Homocysteine and Venous Thrombosis

Elevated plasma total homocysteine concentration is a risk factor for venous thrombosis. The association is well established in patients with homocystinuria irrespective of the genetic etiology and metabolic background. Homocystinuria is a human model of chronic exposure to very high concentrations of plasma homocysteine and reflects an abnormal amino acid metabolism. Elevated homocysteine levels in patients with venous thrombosis have attracted considerable interest because homocysteine is a potentially reversible thrombophilic marker for venous thrombosis. In contrast to homocystinuria, hyperhomocysteinemia is mild and reflects environmental and constitutional factors such as age, intake of B-vitamins, derangements of metabolism, and renal impairment. This review examines the evidence for the relationship of homocysteine with risk of venous thrombosis in homocystinuria and in the general population.

Heterozygous prothrombin 20210G/A mutation, associated with hyperhomocysteinemia, and homozygous methylenetetrahydrofolate reductase 677C/T mutation, in a patient with portal and mesenteric venous thrombosis

We herein report a 34-year-old man who was investigated for severe abdominal pain. Portal vein thrombosis (PVT) and mesenteric vein thrombosis (MVT) were diagnosed. An association with two predisposing factors for thrombosis was noted: (1) heterozygous factor II 20210G/A mutation and (2) homozygous methylenetetrahydrofolate reductase (MTHFR) 677C/T mutation with hyperhomocysteinemia. Our case is of particular interest because the patient reported herein, is homozygote for the MTHFR 677C/T mutation, while the only two other cases reported in the literature with similar gene mutations, were heterozygotes for the mutation.

Thrombomodulin gene polymorphisms or haplotypes as potential risk factors for venous thromboembolism: a population-based case-control study

Dysfunction of the protein C anticoagulant system is associated with venous thromboembolism (VTE) and thrombomodulin (TM) is a critical cofactor within the protein C system. The aim of this study was to test the hypotheses that polymorphisms or haplotypes within the TM gene are common risk factors for VTE. We screened the TM putative promoter, exon and 3'-untranslated region for sequence variations in a random sample (n = 266) of consecutive idiopathic, objectively confirmed non-Olmsted County VTE patients referred to the Mayo Clinic. We then genotyped a sample of Olmsted County, MN residents with a first lifetime, objectively confirmed VTE in the 25-year period, 1966-90 (n = 223), and a sample of Olmsted County residents without VTE (n = 237) for polymorphisms either discovered in the screening population or previously published, and tested for an association of VTE with TM genotype or haplotypes using unconditional logistic regression and generalized linear models, respectively. We also genotyped these Olmsted County cases and controls at 20 'null' genetic maker loci and tested for population admixture. Nine novel and three previously described mutations were identified in the screening population. Mutations within the TM promoter, EGF(1-5), serine/threonine-rich, transmembrane, and cytoplasm regions were absent or uncommon. TM845G-->A (Ala25Thr; lectin region), TM2136T-->C (Ala455Val; EGF(6) region), TM2470C deletion (3'-untranslated region), and 4363A-->G (3'-flanking region) were more common, but were not associated with VTE by genotype or haplotype. Null genetic marker allele frequencies did not differ significantly among cases and controls. We conclude that polymorphisms or haplotypes within the TM gene are not common risk factors for incident VTE.

Fibrinogen polymorphisms TaqI, HaeIII and BclI are not associated with a higher risk of deep vein thrombosis

High fibrinogen is recognised as a risk factor for atherosclerosis. It seems that high fibrinogen is also a risk factor for deep vein thrombosis (DVT). It has been shown that certain polymorphisms in fibrinogen genes can influence the fibrinogen level. In this study, fibrinogen levels and the frequency of the polymorphisms TaqI, HaeIII and BclI were studied in 114 patients with DVT and 244 healthy subjects. In non-smokers, fibrinogen levels above 5 g/l were associated with an increased risk of DVT (odds ratio 3.3, 95% confidence interval 1.6-7.0). The frequencies of common alleles were similar in patients and healthy subjects for all polymorphisms. An association between fibrinogen levels and the polymorphisms TaqI, HaeIII and BclI was found in healthy subjects, but not in the patients. It was concluded from these data that the polymorphisms TaqI, HaeIII and BclI are not major risk factors for DVT.

The occasional venous thromboses seen in patients with severe (homozygous) FXII deficiency are probably due to associated risk factors: a study of prevalence in 21 patients and review of the literature

According to our personal experience and to the study of the literature, 11 cases of venous thrombosis have been described as sporadic reports in patients with severe (homozygous) factor XII (FXII) deficiencies. In every cases but 4, associated risk factors were found to be present (pregnancy, post-partum period, surgery, trauma, in dwelling catheter, AT deficiency, heterozygous factor V Leiden, Burger's disease). In some instances more then one condition was present. The four patients for whom no information is supplied, were cases gathered from old and logically incomplete files and therefore the existence of associated risk factors cannot be excluded. The papers which investigated the presence of venous thrombosis in cohorts of patients with homoxygous FXII deficiency demonstrated the occurrence of venous thrombosis in 2 additional cases out of a total of 63 patients investigated. In these latter cases thrombosis occurred during pregnancy. This brings the total number of patients with FXII deficiency who showed a venous thrombosis to 13. Only a few of these patients were investigated for the presence of concomitant congenital prothrombotic conditions. The conclusion of the study seem to suggest that the role played by FXII deficiency in the pathogenesis of venous thrombosis is minor, if any.

The optimal duration of secondary thromboprophylaxis in patients with venous thromboembolism. The importance of thrombophilia screening

Venous thromboembolism is a chronic disease with an annual incidence of recurrence of 5 to 10%. Patients with venous thrombosis should be treated with anticoagulants for at least 3 months. The optimal duration of anticoagulation entails balancing the risk of recurrence against the risk of treatment-associated bleeding. Candidates for extended anticoagulation are patients with a high risk of recurrence. The risk of recurrence is increased in patients with antithrombin deficiency, the lupus anticoagulant, homozygous F V Leiden, combined defects, high F VIII, high F IX, high TAFI, hyperhomocysteinemia or more than one episode of thrombosis. The risk of recurrence is low in patients with venous thrombosis secondary to surgery or trauma. Routine thrombophilia screening is aimed at identifying patients who could benefit from extended anticoagulation. This population consists of patients with venous thrombosis at a young age, an unprovoked episode of venous thrombosis, patients with a strong positive family history or patients with recurrent venous thrombosis. Screening should comprise antithrombin determination and the search for the lupus anticoagulant. Patients harbouring one of these defects are at high risk of recurrence and most likely will profit from prolonged anticoagulation. The clinical relevance of new treatment strategies such as extended low-intensity warfarin or administration of the direct thrombin inhibitor (xi-)melagatran is at present unclear.