The thrombophilic screening (factor V Leiden mutation, prothrombin gene mutation, inherited deficiencies for protein C, protein S and antithrombin, anticardiolipin antibodies, lupus anticoagulant antibodies, paroxysmal nocturnal hemoglobinuria), including V617F JAK2 mutation, was negative. The gene discussed is PROS1; the disease is paroxysmal nocturnal hemoglobinuria.