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Objective:To clarify the prevalence and clinical characteristics of neuromyelitis optica spectrum disorders (NMOSD) in Japan and compare them with those in other ethnic populations.Methods:Data processing sheets were sent to all related institutions in northern Japan and were collected from April to May 2016. Prevalence was determined on March 31, 2016, using the 2015 International Panel for NMO Diagnosis criteria.Results:The crude prevalence was 4.1/100,000 (95% confidence interval 2.2–6.9) for NMOSD in northern Japan, with a significantly higher number of female than male patients (female: male 12:2). The positivity for anti-aquaporin-4 antibody was 78.6%, and the mean age at onset was 45.2 years. All patients were subjected to preventive therapy in the form of treatment with steroids or immunosuppressive agents.Conclusions:Our results showed that the prevalence of NMOSD in the Japanese population is similar to that in Caucasians.

Background: Oligoclonal IgG bands (OCB) are present in most patients with MS in Western countries; however, in Japanese MS patients, the OCB-positive rate is not as high. A relationship between immunogenetic backgrounds, namely, human leukocyte antigen (HLA) DR2 and DR4 positivity, and OCB production in MS patients from Hokkaido, the northernmost island of Japan, has been previously suggested by the authors.Objectives: To investigate the role of OCB in Japanese MS and to verify the interaction between immunogenetic backgrounds and OCB positivity.Methods: OCB, DR2(15), and DR4 positivity were studied in 45 patients with newly diagnosed MS. In addition to confirming the authors’ previous findings, the clinical and demographic features, MRI findings, OCB positivity, and DRB1*15 and DRB1*04 polymorphisms of an expanded data set of 99 MS patients were investigated by using multivariate analysis. Patients with opticospinal MS (OS-MS) were excluded from this study.Results: A relatively low OCB-positive rate (53.3%), HLA-DR15 association with OCB-positive MS (p = 0.0044), and DR4 association with OCB-negative MS (p = 0.0410) were confirmed. DR15 was not associated with OCB-negative MS. Demographic features, disease course, and disability were similar in the OCB-negative and OCB-positive group, whereas there was a preponderance of women in the OCB-positive group. An independent negative association of DRB1*0405 (p = 0.0021, adjusted odds ratio = 0.21) with OCB positivity was found.Conclusions: MS is heterogeneous in its association with HLA alleles, and based on the immunogenetic differences, the MS patients in this population include at least two HLA-related subpopulations with and without OCB.

A 74-year-old man had radiculitis in the left lower extremity for 1 year. He had undergone radical prostatectomy for prostatic adenocarcinoma 8 years previously. MRI and fludeoxyglucose (FDG)-PET revealed abnormal swelling and FDG uptake …