[Evaluating the origin of thrombophilia: indications and implementation].

The overall incidence per year of deep vein thrombosis is about one per thousand, but may be much higher in the presence of certain clinical risk factors such as advanced age, immobilization, surgical procedures, pregnancy, puerperium, use of oral contraceptive agents and malignancy. Moreover, homocystinuria, nephrotic syndrome, systemic lupus erythematosus and hematological disorders such as paroxysmal nocturnal hemoglobinuria or myeloproliferative syndromes predispose to thrombotic disease. Evaluation of the patient with thromboembolism should include detailed history, clinical examination and laboratory investigation to exclude these secondary thrombophilic states. Primary or hereditary thrombophilia is suspected mainly in patients suffering from (venous) thromboembolism at an early age (< 45 years), especially if recurrent and/or familial thrombosis is present. Hereditary thrombophilia may be due to deficiency of antithrombin III, protein C, protein S or plasminogen, some other defects being less well-established prethrombotic risk factors. These currently recognized primary prethrombotic molecular defects are found in 10 to 30% of patients with idiopathic thromboembolism. In the majority of cases the cause of thrombosis remains unknown.