Bortoli R et al. - SLE activity seems to be associated with the production of antibodies directed against FXI, which may cause important coagulopathies, especially bleeding events. The inhibitor disappeared after immunosuppressive therapy for SLE in most cases, suggesting that the appearance of this inhibitor is immune mediated. Although the majority of cases with the FXI inhibitor are not fatal, it should be suspected and investigated in SLE patients, especially those with abnormal clotting tests.