Several abnormal blood constituents have been implicated in the thrombogenesis in BD, with an emphasis given in certain procoagulant factors (factor V Leiden and prothrombin mutations, MTHFR polymorphisms, hyperhomocysteinemia, and antiphospholipid antibodies), but the results of the related researches are controversial (Table 6); Gül et al. found a positive association between FV Leiden and FII G20210A mutations with venous thrombosis in BD in Turkish patients [8, 9], whereas Silingardi et al. did not confirm these results in Italian patients [10]. This evidence concerns the gene MTHFR and hyperhomocysteinemia.