Rituximab (RTX) is a monoclonal antibody targeting the B-cell CD20 surface antigen used as a prophylactic treatment for Aquaporin 4-immunoglobulin G (AQP4-IgG)-positive neuromyelitis optica spectrum disorder (NMOSD). However, a consensus regarding dosage and maintenance intervals is lacking, and the effects of regular/irregular use on disease recurrence and prognosis, and the risk factors associated with clinical relapse, remain unclear. Therefore, we investigated the efficacy/safety of regular RTX use in patients with NMOSD, and explored risk factors associated with clinical relapses. Data from 106 patients with NMOSD were retrospectively collected from January 5, 2016, and March 1, 2023. Patients were categorized as regular/irregular RTX use, with the latter defined by two intervals of >
9 months, or a single interval of >
12 months, without B-cell monitoring. Compared to the regular treatment group, irregular treatment group showed significant higher annual recurrence rate (ARR) (p = 0.033), Expanded Disability Status Scale (EDSS) score (p = 0.041), and proportions of severe relapse (p = 0.006). In regular RTX use group, the cumulative relapse risk after RTX treatment was significantly lower (p <
0.001). When only considering relapses occurring more than 1 month after starting RTX treatment, 82.3% (51/62) of AQP4-IgG + NMOSD were relapse-free. Independent risk factors of relapse included serum AQP4-IgG titer ≥ 320 at initial disease onset, and severe demyelinating episodes in the first attack. There were no severe side effects. Regular RTX treatment significantly reduces the ARR, incidence of severe relapse, and disability risk in patients with NMOSD.