Efficacy and Safety of Low-Dose Rituximab in Anti-MuSK Myasthenia Gravis Patients: A Retrospective Study

Abstract

Purpose To evaluate the efficacy and safety of low dosages of rituximab (RTX) in the treatment of MuSK-antibody-positive MG patients. Patients and Methods We retrospectively analyzed the data of MuSK-antibody-positive MG patients who were treated with low dosages of RTX from January 2018 to October 2021. The long-term treatment response to RTX was assessed by Myasthenia Gravis Foundation of America (MGFA) post-interventional status (PIS), Myasthenia Gravis Status and Treatment Intensity (MGSTI), dosage of steroid, MG-related activities of daily living (MG-ADL) and myasthenic muscle score (MMS) at the end of follow-up. Results Clinical improvement was observed in all eight patients with follow-up for 8 to 29 months after treatment. At the last visit, complete stable remission had been achieved in one patient, pharmacologic remission in three patients, minimal manifestations status in three patients and improved in one patient based on the MGFA-PIS criteria. MGSTI level 2 or better had been reached in six (75%) patients at the last visit. The steroid dosage decreased from 60 mg at baseline to 15 mg at the last follow-up (p = 0.011). The average MG-ADL score decreased from 11 (range 7 to 15) to 0 (range 0 to 3; p = 0.011), and the MMS improved from 38.5 (range 24 to 60) to 100 (range 90 to 100; p = 0.012). These differences were all statistically significant. During RTX treatment and subsequent follow-up, 1 patient reported minor post-infusion malaise. Conclusion Low-dose RTX is effective and safe for treating anti-MuSK antibody positive MG patients. A long-term response is observed after treatment. Larger prospective studies are required to provide further evidence.

A Case Report of MuSK Antibody-Positive Myasthenia Gravis

“…Evidence supports the use of monoclonal antibody therapy such as rituximab as an early therapeutic option in MuSK-MG patients with poor responses to steroids [ 1 , 7 , 8 ]. Patients with MuSK-MG receiving rituximab show sustained clinical improvement, as in our case.…”

“…The use of acetylcholinesterase inhibitors for symptomatic treatment is generally unsatisfactory in MuSK-MG patients. Steroids and immunosuppression therapy have a better response, and monoclonal antibodies such as rituximab therapy showed greater and sustained outcomes in MuSK-MG patients [ 1 , 7 , 8 ].…”

Immunotherapies in MuSK-positive Myasthenia Gravis; an IgG4 antibody-mediated disease

“…One patient relapsed among three patients whose CD27+ B-cell counts were >0.05% at 6 months. On the other hand, clinical relapses occurred even though B cells were depleted ( 172 ). Collectively, we could not reach a definite conclusion regarding the B lymphocytes number in patients and the recurrence of clinical symptoms.…”

Case report: Complex paraneoplastic syndromes in thymoma with nephrotic syndrome, cutaneous amyloidosis, myasthenia gravis, and Morvan’s syndrome

“…The patient was diagnosed with Morvan’s syndrome and treated with IVIG at a dose of 0.4 g/kg/day for 5 days and oral steroids; however, his symptoms of myokymia and insomnia did not improve 1 month later. Considering that the patient’s immune test indicated that he was in an immunosuppressive state at the time, he was treated with low-dose rituximab ( 7 , 8 ) at a dose of 100 mg/week for 4 weeks. During the follow-up 1 month later, the muscle twitching, limb pain, and insomnia symptoms were significantly improved.…”