BackgroundNeurological disorders with IgG antibodies against myelin-oligodendrocyte glycoprotein (MOG-IgG) have been increasingly recognised as a new type of neuroinflammatory disorder.ObjectiveThe study aimed to identify regional and ethnic differences in clinical profiles of MOG-IgG–associated disorders between East Asian (Japanese) and Caucasian (German) patients.MethodsDemographic, clinical and therapeutic data from 68 MOG-IgG–positive adults were collected (Japanese, n=44; German, n=24).ResultsAge and sex were similar between cohorts, with optic neuritis occurring most frequently at onset (Japanese: 61%; German: 58%). However, Japanese patients had a lower annualised relapse rate (0.4 vs 0.8, p=0.019; no relapse, 64% vs 25%, p=0.002) and lower Expanded Disability Status Scale score at the last visit (1.0 vs 2.0; p=0.008), despite similar follow-up periods (mean, 73.9 months vs 73.4 months), than those of German patients, respectively. Cerebral syndromes were more common (27% vs 4%; p=0.021) and myelitis less common (21% vs 50%; p=0.012) in Japanese than in German patients, respectively. Japanese patients were more commonly treated with long-term corticosteroids (73%), whereas German patients were more commonly treated with rituximab or other immunosuppressants (63%).ConclusionsAmong patients with MOG-IgG, Japanese tended to have a monophasic milder disease, whereas the majority of German patients had a relapsing course and more frequent myelitis, findings compatible with neuromyelitis optica spectrum disorder. Although the attack-prevention treatment regimens were considerably different, genetic and environmental factors may be important to determine clinical phenotypes and disease activity.