Contribution of natural anticoagulant and fibrinolytic factors in modulating the clinical severity of haemophilia patients.

The role of natural anticoagulants, fibrinolytic cascade factors and common prothrombotic gene polymorphisms in modulating disease severity were studied in 35 'clinically mild' and 37 'clinically severe' haemophilia patients with severe factor VIII or IX deficiency (<0.01 IU/ml). Strong association of deficiencies of proteins C and S, antithrombin III, tissue factor pathway inhibitor and tissue plasminogen activator, together with factor V Leiden and endothelial protein C receptor 23 bp insertion polymorphisms were observed in the 'clinically milder' group as compared with the 'clinically severe' group. These results indicate a synergistic modulation of bleeding tendency in haemophilia patients by factors in the anticoagulant and fibrinolytic systems.