Induction intravenous cyclophosphamide followed by maintenance oral immunosuppression in refractory myasthenia gravis

Introduction: Myasthenia gravis (MG) can be refractory to conventional immunotherapy. We report on the efficacy and durability of intravenous (IV) remission-induction cyclophosphamide (CYC) followed by oral immunosuppression in refractory MG. Methods: We identified 8 patients from our medical records with moderate or severe refractory MG who were treated with 6 cycles of IV CYC (0.75 g/m²) every 4 weeks followed by oral immunosuppression. Results: Six patients improved within 3 months of treatment. Four patients remained in clinical remission (mean follow-up 31 months). Two patients responded partially, and 1 patient relapsed after 11 months. Two patients were non-responders. CYC was well tolerated. Acetylcholine receptor antibody levels remained below pretreatment levels in patients in clinical remission. The leukocyte nadir was lower in CYC responders. Conclusions: Remission-induction IV CYC followed by oral immunosuppression is a rapid, effective, and durable treatment for refractory MG. Adding a post-CYC immunosuppressant may account for low relapse rates compared with other published series.