PROS1 and thrombophilia: Among the most common causes of primary thrombophilia, mutations in the methylenetetrahydrofolate reductases (MTHFR) enzyme, protein S (PS) and protein C (PC) deficiency, presence of lupus anticoagulant/antiphospholipid syndrome, mutations that increase risk of a hypercoagulable state like Factor V Leiden (FVL), and mutations of the prothrombin gene have been reported [2].