An extensive screening for hereditary thrombophilia (factor V Leiden mutation, prothrombin gene mutation, and inherited deficiencies for protein C, protein S and antithrombin) and acquired pro-thrombotic disease (myelo-proliferative disorders, anticardiolipin antibodies, lupus anticoagulant antibodies, paroxysmal nocturnal hemoglobinuria) was carried on. The gene discussed is F5; the disease is paroxysmal nocturnal hemoglobinuria.