Increasing data are available on the use and efficacy of rituximab in patients with anti-MuSK-positive MG patients, especially who are steroid-dependent or unresponsive to traditional immunosuppressive agents.

To evaluate clinical characteristics and treatment response of adult myasthenia gravis (MG) patients with anti-muscle-specific tyrosine kinase (MuSK) antibody, treated with rituximab.

We retrospectively recruited 16 anti-MuSK-positive MG patients who were on rituximab treatment between January 2010 and September 2021. Rituximab was given 1000 mg/day twice, 15 days apart. Maintenance treatment was administered at intervals of 3-6 months depending on clinical evaluation. The outcome was assessed by Myasthenia Gravis Foundation of America (MGFA) classification and Myasthenia Gravis Status and Treatment Intensity (MGSTI) score. Besides, anti-MuSK antibody titters were measured after treatment.

Sixteen patients who were followed at least 14 months after the treatment were included to the study. Twelve patients were female, and the mean age was 42.5±17.3 years. The median time between disease onset and  rituximab treatment was 2.4 (0.5-36.5 years) years. Maximum disease severity before treatment was between MGFA IIIb and V (Level 2–6 according to MGSTI).  MGSTI scores were ≤ 1 in 13 patients after the treatment. Clinical stabilization was achieved (remission/minimal manifestation according to MGFA post-intervention status), corticosteroids and other immunosuppressive treatments were gradually discontinued in these patients. Lastly, anti-MuSK-antibody titers became negative in 10 patients whereas still positive in 3 patients after rituximab.

Rituximab is an effective treatment in anti-MuSK-positive MG patients unresponsive to conventional immunosuppressive treatment. Furthermore, our results support the inhibition of antibody production by rituximab treatment.