Resistant myasthenia gravis and rituximab: A monocentric retrospective study of 28 patients

This retrospective study evaluated the efficiency and tolerance of rituximab in the management of resistant myasthenia gravis (MG). All patients who received rituximab for the treatment of MG between 2004 and 2015 at Pitié-Salpétrière University Hospital (Paris, France) were included. The efficacy of rituximab was evaluated every 6 months by the myasthenic muscle score (MMS), the Myasthenia Gravis Foundation of America - Clinical Classification (MGFA-CC), the MGFA Therapy Status and the Postintervention Status (PIS). All rituximab-related side effects were noted. Twenty-eight patients were included: 21 with anti-acetylcholine receptor antibodies, 3 with anti-muscle-specific tyrosine kinase antibodies and 4 seronegatives. The mean age at day 1 of RTX was 50.6 ± 12.0 years. Patients previously received 1-4 immunosuppressants. The mean follow-up was 27.2 months (range: 6-60 months). The mean total dose of rituximab was 4.8 ± 2.5 g. The initial median MMS (58.8 points) improved significantly at M6 (74.5 ± 15.0 points; p < 0.0001) and remained stable thereafter: at M12: 75.9 ± 14.0 points (p = 0.00014), at M36: 72.5 ± 13.1 points (p = 0.0013). Among 16 patients with initial severe symptoms (MGFA-CC class IV), 14 improved. The PIS showed efficacy in about 50% of patients: at M6, 12/28 (43%) patients were considered improved. This benefit remained stable thereafter: at M12: 12/24, at M24: 7/17, at M36: 6/12. One patient developed a delayed progressive multifocal leukoencephalopathy. Based on the PIS, rituximab may be efficient in 50% of patients with MG resistant to immunosuppressants.