Acquired factor XI inhibitor in systemic lupus erythematosus--case report and literature review.

OBJECTIVES: Rare patients with systemic lupus erythematosus (SLE) patients exhibit anticoagulants that interfere in the earlier stages of the intrinsic coagulation pathway, such as those involving factor XI (FXI). The objectives of our study were to describe the presence of an acquired inhibitor to FXI causing a life-threatening bleeding disorder in an SLE patient and to review the association of this coagulopathy with SLE.
METHODS: We describe the clinical presentation of an SLE patient with an acquired FXI inhibitor. We reviewed the scientific literature using the MEDLINE database searching the following combinations of terms: "SLE and Factor XI," "SLE and Factor XI inhibitor," and "Factor XI inhibitor," from 1964 to 2007.
RESULTS: A 20-year-old woman with a 6-year history of SLE was admitted to the hospital because of severe life-threatening abdominal bleeding due to a ruptured ovarian cyst. This hemorrhagic event was related to the presence of an FXI inhibitor. We reviewed another 13 SLE patients with this condition, 8 of whom had bleeding events. Most patients had manifestations of active SLE, and prednisone was used as the primary treatment.
CONCLUSIONS: 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.