The Japan Neuromyelitis Optica Spectrum Disorders/Myelin Oligodendrocyte Glycoprotein Antibody‐Associated Disease Registry: Background Analysis of the Initial 116 Cases

Objectives To describe the baseline clinical characteristics of patients with neuromyelitis optica spectrum disorders (NMOSD) and myelin oligodendrocyte glycoprotein antibody‐associated disease (MOGAD) enrolled in the Japan NMOSD/MOGAD Registry (UMIN000051988) and to assess their representativeness of both conditions in the Japanese population. Methods This prospective multicenter observational registry study was conducted at 10 neurology referral centers in Japan. Patients with NMOSD or MOGAD were enrolled based on established diagnostic criteria. Clinical data, treatment history, and biological samples were collected annually. The present analysis includes patients registered between December 20, 2023 and July 31, 2024. Descriptive statistics were used to summarize the clinical data. Results A total of 116 patients (NMOSD, n = 110; MOGAD, n = 6) were analyzed. Among NMOSD patients, the mean age at onset was 50.0 years, and 89.1% were female. Most were anti‐aquaporin 4 antibody seropositive (93.6%). The median Expanded Disability Status Scale (EDSS) was 3.5%, and 67.3% had a relapsing course. Biologic agents were used in 63.6% of NMOSD patients. Among MOGAD patients, the mean age at onset was 27.3 years, and all were anti‐myelin oligodendrocyte glycoprotein antibody seropositive. Visual symptoms predominated, and the median EDSS was 2.25. Conclusions The clinical characteristics of NMOSD patients in the registry are consistent with prior epidemiological data, supporting the representativeness of the cohort. The high rate of biologic agent use reflects current treatment practices in Japan. In contrast, the representativeness of MOGAD cases could not be evaluated due to their limited number, highlighting the need to further accumulate cases.