During the past decade idiopathic venous thromboembolism has become a separate entity, a chronic illness which has required prolonged anticoagulation and other prevention strategies to avoid recurrences. This article reviews recent developments regarding unprovoked venous thromboembolism and its relation with thrombophilia. In the beginning, the latest definition of idiopathic venous thromboembolism is presented. The article continues with statistics about thrombophilia, related venous thromboembolism, and a classification of major thrombophilic factors according to their intrinsic risk of thrombosis and of thrombotic recurrences. Great interest is given to the predictors of recurrence and the importance of prolonged anticoagulation is underlined. The antiphospholipid antibody syndrome, the most common acquired thrombophilia, is presented separately. The revised diagnosis criteria are discussed. Some characteristics of the antiphospholipid syndrome are worth presenting: the risk of both venous and arterial thrombosis, the high risk of thrombotic recurrence and the diversity of antiphospholipid antibodies.

Patients experiencing idiopathic venous thromboembolic event have a great risk of recurrence, and highly benefit from long time anticoagulation. Natural coagulation inhibitors deficiencies, homozygous factor V Leiden and prothrombin G20210A and the antiphospholipid syndrome, increase the risk of first venous thrombosis and their recurrences and require adequate prevention.

Abbreviations: VTE–venous thromboembolism, HRT–hormone replacement therapy, AVK–antivitamin K, FVL–factor V Leiden, PT G20210A–prothrombin G20210A, TAFI–thrombin activatable fibrinolysis inhibitor, PAI–1–plasminogen activator inhibitor 1, T–PA–tissue plasminogen activator, APS–antiphospholipid syndrome, LA–lupus anticoagulant, Abeta2GP1–anti beta2 glycoprotein 1.