Associated thrombophilic defects in essential thrombocythaemia:: their relationship with clinical manifestations

In order to assess the contribution of genetic and acquired thrombophilic defects in the risk of thrombosis in essential thrombocythaemia, we evaluated the prevalence of factor V Leiden, prothrombin G20210A and methylenetetrahydrofolate reductase C677T polymorphisms, homocysteinemia, protein C, protein S and antithrombin III levels, activated protein C resistance, lupus anticoagulant, anticardiolipin, anti-β2 glycoprotein I and antiphospholipid antibodies in 60 ET patients, 17 with thrombosis and 23 with microvascular disturbances. The allele frequency of prothrombin G20210A polymorphism in ET was higher than in controls (5% vs. 0.7%, p = 0.04) while no differences were found for factor V Leiden (0.8% vs. 1.4%, p = 0.5) nor methylenetetrahydrofolate reductase C677T polymorphism (35.8% vs. 34.3%, p = 0.9). Deficiency of protein C, protein S and antithrombin III levels were not found in any patient although median protein S levels were lower than in controls (89% vs. 110%, p = 0.007). Two patients had activated protein C resistance, six harboured antiphospholipid antibodies and five had hyperhomocysteinemia. Although thrombophilic conditions were detected in one third of our patients with ET, no correlation was found between these prothrombotic factors and the development of thrombosis. Routine screening for these conditions in ET may not be justified.