Objective: This study aimed to investigate the efficacy and safety of low-dose rituximab (RTX) in the treatment of neuromyelitis optica spectrum disorders (NMOSD) patients. Methods: NMOSD patients were treated with RTX at ~25% of the standard dose. The annualized relapse rate (ARR), expanded disability status scale (EDSS) score, visual function system scale (VFSS) and length of spinal cord lesions before and after treatment were statistically compared. The dynamic changes in the proportion of CD19⁺ B lymphocytes after treatment were monitored, and adverse reactions were recorded. Results: In total, 36 NMOSD patients who received a low-dose RTX treatment (375-mg/m² induction dose and 500 mg every 6 months) were recruited. The mean follow-up time after the RTX treatment was 19.83 ± 7.74 months. After the treatment, the ARR decreased from 1.97 ± 1.93 to 0.12 ± 0.32, the EDSS score decreased from 3.43 ± 1.49 to 3.10 ± 1.88, and the spinal cord lesion length decreased from 5.54 ± 3.96 to 4.31 ± 3.73. These differences were all statistically significant. The subgroup analysis of the patients who had previously received non-steroidal immunosuppressants (NSISs) (n = 20) showed that after the RTX treatment, the ARR decreased from 0.66 ± 0.51 to 0.08 ± 0.26, the EDSS score decreased from 3.65 ± 1.22 to 3.40 ± 1.99, and the spinal cord lesion length decreased from 5.68 ± 3.73 to 4.21 ± 3.58. These differences were all statistically significant. The VFSS scores did not show a significant change. The Kaplan-Meier analysis showed that low-dose RTX significantly delayed recurrence, which was also observed in the subgroup analysis of patients who previously received NSISs. Five relapses in 5 cases were noted after the low-dose RTX administration, and the percentage of CD19⁺ B cells remained < 1% in 3 cases during relapse. During the RTX treatment and subsequent follow-up, 8 (22.2%) patients reported adverse reactions, all of which were minor. Conclusion: Low-dose RTX is an effective and safe treatment method for NMOSDs. This method is worth popularizing in developing countries or regions, especially in areas where RTX is not covered by medical insurance.

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