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Research Article: Efficacy and safety of low-dose rituximab in MuSK antibody-positive myasthenia gravis: a single-center retrospective study

Date Published: 2026-08-24

Abstract:
Rituximab (RTX) is increasingly used for refractory myasthenia gravis (MG), particularly muscle-specific kinase antibody-positive MG (MuSK-MG). However, the optimal dosing regimen remains to be standardized, and conventional high-dose protocols may increase treatment burden, cumulative exposure, and infection-related concerns. This study evaluated the clinical efficacy, safety, and immunological effects of a low-dose RTX regimen in patients with MuSK-MG. We retrospectively analyzed 35 patients with MuSK-MG who received low-dose RTX at the First Affiliated Hospital of Guangzhou University of Chinese Medicine between January 1, 2017 and August 1, 2025. RTX was administered as 100?mg on day 1 and 500?mg on day 2, and the regimen was repeated every 6?months. All patients received at least two treatment cycles. Clinical outcomes were assessed using Myasthenia Gravis Activities of Daily Living (MG-ADL) scores at baseline and at 3, 6, and 12?months after treatment. Secondary outcomes included Myasthenia Gravis Foundation of America post-intervention status (MGFA-PIS), adverse events, and peripheral CD19+ B-cell percentages in 24 patients. The mean baseline MG-ADL score was 9.5?±?5.6 and decreased to 2.1?±?2.3 at 3?months, 1.0?±?1.8 at 6?months, and 0.5?±?0.9 at 12?months (all p <?0.001 vs. baseline). At 3, 6, and 12?months, 21 (60.0%), 25 (71.4%), and 28 (80.0%) patients achieved minimal manifestation status (MMS) or better was 6 months, respectively. Kaplan–Meier analysis showed a median time to MMS or better of 6?months. Both the bulbar involvement (BI) and non-bulbar involvement (non-BI) subgroups showed significant clinical improvement, although the trajectories of MG-ADL improvement differed between subgroups. In the 24 patients with available immunological data, the median CD19+ B-cell percentage decreased from 12.6% before treatment to 0.30% at 6?months ( p <?0.001). Adverse events were mild, and no serious infusion reactions, severe infections, or hepatic or renal dysfunction were observed. Low-dose RTX was associated with rapid and sustained clinical improvement and effective peripheral B-cell depletion in patients with MuSK-MG, with acceptable tolerability. These findings support low-dose RTX as a potential therapeutic option for MuSK-MG, although prospective multicenter studies with standardized dosing and longer follow-up are needed.

Introduction:
Rituximab (RTX) is increasingly used for refractory myasthenia gravis (MG), particularly muscle-specific kinase antibody-positive MG (MuSK-MG). However, the optimal dosing regimen remains to be standardized, and conventional high-dose protocols may increase treatment burden, cumulative exposure, and infection-related concerns. This study evaluated the clinical efficacy, safety, and immunological effects of a low-dose RTX regimen in patients with MuSK-MG.

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