PC and myeloproliferative disorder: Major causal factors include myeloproliferative neoplasm (MPN), factor V Leiden (FVL) mutation, prothrombin G20210A gene mutation, antiphospholipid antibodies, hyperhomocysteinemia, paroxysmal nocturnal hemoglobinuria, antithrombin (AT), protein C (PC), protein S (PS) deficiencies, and others [1, 2].