Long-lasting treatment effect of rituximab in MuSK myasthenia

Objective: Rituximab has emerged as an efficacious option for drug-resistant myasthenia gravis (MG). However, reports published only describe the short-term follow-up of patients treated and little is known about their long-term clinical and immunologic evolution. Our objective was to report the clinical and immunologic long-term follow-up of 17 patients (6 MuSK +/- MG and 11 AChR +/- MG) and compare the response between AChR +/- MG and MuSK +/- MG patients. Methods: Myasthenia Gravis Foundation America postintervention status and changes in treatment and antibody titers were periodically determined. Lymphocyte subpopulations, total immunoglobulin, immunoglobulin G (IgG) anti-MuSK subclasses, and anti-tetanus toxoid IgG before and after treatment were also studied. Results: After a mean post-treatment period of 31 months, 10 of the AChR +/- MG patients improved but 6 of them needed reinfusions. In contrast, all MuSK +/- MG patients achieved a remission (4/6) or minimal manifestations (2/6) status and no reinfusions were needed. Consequently, in the MuSK +/- MGgroup, prednisone doses were significantly reduced and concomitant immunosuppressants could be withdrawn. Clinical improvement was associated with a significant decrease in the antibody titers only in the 6 MuSK +/- MG patients. At last follow-up MuSK antibodies were negative in 3 of these patients and showed a decrease of over 80% in the other 3. Conclusion: In view of the long-lasting benefit observed in MuSK +/- MGpatients, we recommend to use rituximab as an early therapeutic option in this group of patients with MG if they do not respond to prednisone. Classification of evidence: This study provides Class IV evidence that IV rituximab improves the clinical and immunologic status of patients with MuSK +/- MG. Neurology (R) 2012;78:189-193