Prevalence and clinical features of neuromyelitis optica spectrum disorders in northern Japan

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.