No impact of factor IX Ala-10 mutations in acenocoumarol-treated southern Europeans.

Increased risk of bleeding during oral anticoagulant (OA) treatment may be related to mutations in the precursor of coagulation factor IX. Missense mutations at Ala-10 (Ala-10Thre and Ala-10Val) in the factor IX propeptide lead to impaired carboxylation of factor IX. When patients carrying these mutations are treated with coumarins, functional factor IX levels decrease significantly, leading to an excessively prolonged activated partial thromboplastin time (aPTT) and an increased bleeding risk. Mutations at Ala-10 have been described in northern-European patients, but it is not known whether geographical differences play a role in the prevalence of these mutations. We aimed to analyze the prevalence of mutations at Ala-10 in factor IX in southern-European patients on OA treatment. Patients attending the Oral Anticoagulant Unit of the Hospital Clinic were prospectively included. The aPTT was determined at their normal International Normalized Ratio (INR) control. When the aPTT was excessively prolonged for the INR value, determination of factor IX and genotyping for Ala-10 mutations was performed. A total of 2360 patients were included (1289 men, 1071 women; mean age, 70.5 +/- 12.1 years). Twenty-four patients (16 men, eight women; mean age, 61.0 +/- 16.2 years) had an aPTT over that expected for the INR. The mean aPTT was 69.6 +/- 16.2 s. Only one patient presented with a factor IX level lower than 10%. None of the 24 patients carried mutations at Ala-10. Mutations at Ala-10 in factor IX were non-existent in the southern-European population analyzed, and thus, do not represent a relevant cause of bleeding during OA treatment.

Effects of beta2-glycoprotein I and monoclonal anticardiolipin antibodies in platelet interaction with subendothelium under flow conditions.

OBJECTIVE: To evaluate whether the effect of human monoclonal anticardiolipin antibodies (aCL) on platelet interaction with the subendothelium under flow conditions is dependent on beta(2)-glycoprotein I (beta(2)GPI). METHODS: Three monoclonal IgM aCL with anti-beta(2)GPI activity (TM1B3, GR1D5, and EY2C9) obtained from patients with antiphospholipid syndrome, a monoclonal aCL with lupus anticoagulant activity but without anti-beta(2)GPI activity (FRO) obtained from a patient with a splenic lymphoma, and a control monoclonal IgM without aCL activity were used. TM1B3, GR1D5, EY2C9, FRO, and control IgM (30 microg/ml) were added to reconstituted blood containing gel-filtered platelets (200 x 10(9)/liter), factor VIII (100 units/dl), and fibrinogen (1.5 gm/liter). Samples were perfused (wall-shear rate 800 seconds(-1)), with and without the addition of purified beta(2)GPI (20 microg/ml), through annular chambers containing collagen-rich denuded vascular segments, and the percentages of surface covered by platelets and by thrombi were evaluated. RESULTS: No differences in the percentages of surface covered by platelets and by thrombi were observed among samples with TM1B3, GR1D5, EY2C9, FRO, and control IgM added when reconstituted blood samples without beta(2)GPI were used. However, a significant increase in the percentage of surface covered by platelets was observed in the presence of TM1B3, GR1D5, and EY2C9 but not in the presence of FRO when samples containing beta(2)GPI were used. Increased thrombi formation was induced by TM1B3 and GR1D5 but not by EY2C9 or FRO in samples with added beta(2)GPI. CONCLUSION: Monoclonal aCL require anti-beta(2)GPI activity to promote platelet interaction with the subendothelium under flow conditions.

Pharmacogenetics of acenocoumarol: cytochrome P450 CYP2C9 polymorphisms influence dose requirements and stability of anticoagulation.

BACKGROUND AND OBJECTIVES: Cytochrome P4502C9 (CYP2C9) is the main enzyme implicated in coumarinic metabolism. Variant alleles, CYP2C9*2 and CYP2C9*3, have been related to decreased enzymatic activity, but their clinical relevance in acenocoumarol metabolism has not been established. We investigated CYP2C9 polymorphisms in relation to acenocoumarol dose requirement, stability of anticoagulation and bleeding. DESIGN AND METHODS: CYP2C9 genotyping was performed in 325 acenocoumarol-treated patients (INR target between 2.0 and 3.0) and in an additional group of 84 patients with repeated bleeding. RESULTS: Patients with the wild-type CYP2C9*1/*1 genotype (n=169) required a higher maintenance dose of acenocoumarol (17.1 8.7 mg/week) than did patients with the CYP2C9*2 (14.6 6.4 mg/week, p<0.05, N=97) or the CYP2C9*3 allele (11.2 6.2 mg/week, p<0.001, n=59). Out of 170 patients requiring a low-dose of acenocoumarol (70 years (OR=3.73, 95%CI=2.29-6.08, p<0.001), and the CYP2C9*3 allele (OR=4.75, 95%CI=2.36-9.55, p <0.001). Carriers of CYP2C9*3 spent less time within the therapeutic range (64.7 23.1%) than did patients with the CYP2C9*1/*1 genotype (75.1 22.0%, p<0.01), and more frequently had an INR >4.5 at the initiation of treatment (43.9% vs.11.6%, p<0.001), but did not show repeated bleeding more frequently (19.0% vs.15.5%, p=NS). INTERPRETATION AND CONCLUSIONS: CYP2C9*3 is related to lower acenocoumarol dose requirements, a higher frequency of over-anticoagulation at the initiation of therapy and an unstable anticoagulant response.

Vascular involvement in Behçet's disease: relation with thrombophilic factors, coagulation activation, and thrombomodulin.

PURPOSE: Thrombosis, usually venous, occurs in 10% to 25% of patients with Behçet's disease, but its pathogenesis is poorly understood. We evaluated parameters of hemostasis and their relation with thrombosis in a series of patients with Behçet's disease. SUBJECTS AND METHODS: We studied 38 patients with Behçet's disease (13 with venous thrombosis), 38 patients with venous thrombosis without thrombophilia, and 100 control subjects. Levels or presence of protein C, protein S, antithrombin, methylenetetrahydrofolate reductase C677T, factor V Leiden, prothrombin gene G20210A, antiphospholipid antibodies, plasminogen, tissue-type plasminogen activator (tPA), type-1 tPA inhibitor (PAI-1), PAI-1 4G/5G polymorphism, prothrombin fragment 1+2, plasmin/alpha(2)-antiplasmin complexes, thrombomodulin, and activated factors VII and XII were determined. RESULTS: There were no deficiencies in protein C, protein S, antithrombin, or factor V Leiden in the patients with Behçet's disease, nor was there evidence of most other thrombotic abnormalities. Compared with control subjects, however, the Behçet's disease group had elevated mean (+/- SD) levels of prothrombin fragment 1+2 (2091 +/- 1323 pmol/L vs. 804 +/- 398 pmol/L, P <0.001), plasmin/alpha2-antiplasmin complexes (410 +/- 220 microg/L vs. 214 +/- 92 microg/L, P <0.001), and thrombomodulin (37 +/- 24 ng/mL vs. 27 +/- 10 ng/mL, P <0.001). These levels did not differ between patients with or without thrombosis. CONCLUSIONS: Thrombophilic factors do not seem to explain most thromboses in Behçet's disease. There is increased thrombin generation, fibrinolysis, and thrombomodulin in Behçet's disease, but these abnormalities are not related to thrombosis.