Insights from the differences in clinical profiles of neuroimmune disorders between patients in Japan and those in Western countries

Abstract

Few studies have investigated the differences in the clinical profiles of neuroimmune disorders between patients in Japan and those in Western countries.15 In 1981, Shibasaki et al. first reported the difference in clinical features of multiple sclerosis (MS) between Japanese patients and British patients.2 Japanese patients with MS had a higher prevalence of and more severe visual involvement, and were more likely to have myelitis and brainstem syndrome compared with British patients with MS. Although it is well known that these clinical features are not typical of MS, but are associated with neuromyelitis optica (NMO), the study by Shibasaki et al. and subsequent reports improved our understanding of the clinical features of NMO. Furthermore, the studies showed the presence of a larger ratio of NMO to MS in Japan than that in Western countries. Thus, comparing the clinical profiles of neuroimmune disorders between Japan and Western countries can potentially improve our understanding of the disorders, and the importance of genetic and environmental factors. In collaboration with researchers at Tohoku University, Kitley et al. reported the difference in prognosis in antiaquaporin4 antibodypositive NMO spectrum disorders not only between Japanese and British patients, but also among Asian, white and AfroCaribbean patients.4 Japanese patients generally had a better prognosis than British patients, and Asian patients generally had a better prognosis than AfroCaribbean patients. Recently, we reported the difference in the clinical profiles and prognosis of Japanese and German patients with antimyelin oligodendrocyte glycoprotein antibodyassociated disorders (MOGAD).5 Demographic, clinical and therapeutic data from 73 patients with MOGAD were assessed; 44 patients were from two Japanese centers (Chiba University Hospital and Saitama Medical Center), and 29 were from two German centers (Charité – Universitätsmedizin Berlin and LMU Hospital). Although age, sex and duration of follow up were similar between the two cohorts, Japanese MOGAD patients had a lower annualized relapse rate (0.4 vs 0.8, P = .019) and Expanded Disability Status Scale score at the last visit (1.0 vs 2.0, P = .008) than those of German MOGAD patients. Cerebral syndromes were more common and myelitis was less common in Japanese than in German patients (cerebral syndromes, 27% vs 4% [P = 0.021]; myelitis, 21% vs 50% [P = 0.012]). The Japanese cohort had the highest proportion of longterm corticosteroid treatment (73%), and rituximab or other immunosuppressants were used comparatively more in German cohorts (63%) than other cohorts. We concluded that Japanese MOGAD patients tended to have a milder monophasic disease course, whereas most German MOGAD patients had a relapsing course and more frequent myelitis; these findings were consistent with antiaquaproin4 antibodypositive NMO spectrum disorders. The following are possible explanations for these differences: (i) Japanese treatment regimens mainly consisting of steroids are better than other treatments mainly consisting of rituximab or other immunosuppressants, or (ii) genetic and environmental factors might contribute to clinical phenotypes and disease activity. Although larger prospective studies will be required to confirm the results, and to investigate the association between clinical profiles and genetic backgrounds, we hope this study will inspire further exploration of the pathogenesis of MOGAD.