4. For patients with recurrent CVT, venous thromboembolism (VTE) after CVT, or first CVT with severe thrombophilia (ie, homozygous prothrombin G20210A; homozygous factor V Leiden; deficiencies of protein C, protein S, or antithrombin; combined thrombophilia defects, or antiphospholipid syndrome), lifelong anticoagulation can be considered, with a target INR of 2.0 to 3.0 (Class IIb; Level of Evidence C). Here, PROS1 is linked to Rare hereditary thrombophilia.