Treatment of adult inflammatory myositis with rituximab: an emerging therapy for refractory patients

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.

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.

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.

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.

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.