F5 and paroxysmal nocturnal hemoglobinuria: The prothrombotic conditions most frequently associated with BCS, particularly the classic type, include the following: factor V Leiden mutation, prothrombin gene (PT) mutation, protein C and S deficiency, antithrombin deficiency, APS, hyperhomocysteinemia, and paroxysmal nocturnal hemoglobinuria (PNH) [16].