A venous thrombus can become a life-threatening pulmonary embolism (PE), if a clot formed in the deep veins breaks free and enters the arteries of the lungs.[1] PE is a primary cause of mortality associated with DVT.[2] Known genetic factors of DVT include deficiencies of antithrombin (AT), protein C, protein S, factor V Leiden mutation, and prothrombin G20210A mutation.[2,3] AT deficiency is a major risk factor for venous thromboembolic disorders. The gene discussed is PROS1; the disease is deep vein thrombosis.