Treatment of Adult Inflammatory Myositis With Rituximab An Emerging Therapy for Refractory Patients

Background: Rituximab is a genetically engineered chimeric, murine/human monoclonal antibody directed against the CD20 antigen on B-cells. Recent studies of inflammatory myopathy have shown that B-cells are important in the etiopathogenesis of these diseases, and therefore suggest a role for B-cell depletion therapy in idiopathic inflammatory myopathy. The few case reports and small series that have been published suggest that anti-B-cell therapy is effective for the clinical manifestations of inflammatory myopathy. Objectives: To report our experience using rituximab to treat 3 patients with refractory idiopathic inflammatory myopathy (IIM), and to review and discuss the available literature regarding reported experience using rituximab in treating IIM. Methods: We describe the clinical courses of 3 patients with IIM treated by us with rituximab after unsatisfactory responses to conventional therapy. We performed a search of the English language literature utilizing PubMed, and identified 8 articles that also described the use of rituximab for treatment of IIM. Results: Improvement in our patients was manifested by an increase in muscle strength and decline in creatinine kinase levels in all 3 patients. Recurrent muscle weakness and elevated muscle enzymes occurred in 2 patients postinfusion; retreatment with rituximab resulted in similar clinical improvement. Our experience, and that 20 of 21 patients described in 8 cited reports demonstrate a favorable clinical response in patients treated with B-cell depletion therapy for IIM. Conclusions: Early uncontrolled clinical experience indicates that rituximab may be a valuable therapeutic agent for treatment of refractory IIM. Further investigation regarding the optimal dosing regimen, treatment length, and long-term safety profile of rituximab therapy for IIM is warranted.