Rituximab off label use for difficult-to-treat auto-immune diseases: reappraisal of benefits and risks.

Rituximab is increasingly used off label for difficult-to-treat auto-immune diseases. We reviewed the main case series or clinical studies to identify the best indications of rituximab and the situations at substantial risks for adverse events. Refractory immune thrombocytopenic purpura was the main indication. However, the long term benefit-to-risk ratio of rituximab treatment before or after splenectomy is unknown. A single 375 mg/m2 infusion may be as efficacious as the classical four infusions cycle. Rituximab is the best treatment for cold agglutinin disease. In warm agglutinin auto-immune anaemia, its efficacy has essentially been reported in chronic lymphocytic leukemia (CLL) patients and in children. In CLL patients, lethal adverse events occurred in patients also receiving cyclophosphamide. Rituximab seems to have an interesting benefit-to-risk ratio in Wegener granulomatosis (excepted in granulomatous lesions), HCV-associated symptomatic cryoglobulinemia in patients unresponsive to anti-viral therapy, pemphigus and thrombotic thrombocytopenic purpura. Efficacy and safety data in lupus are difficult to interpret. Serum sickness disease is not exceptional in immune thrombocytopenic purpura (ITP), lupus and sicca syndrome patients. A substantial infectious risk has been reported in pemphigus patients and in post-renal transplant cryoglobulinemia. Double-blind randomised controlled trials and phase IV studies are mandatory in most clinical settings to confirm the overall favourable perception of rituximab benefit to risk ratio.