Prevalence and Relative Proportions of Multiple Sclerosis, Neuromyelitis Optica Spectrum Disorder, and Myelin Oligodendrocyte Glycoprotein Antibody–Associated Disease in the Republic of Korea

OBJECTIVES: To provide the clinically validated, nationwide estimates of multiple sclerosis (MS), neuromyelitis optica spectrum disorder (NMOSD), and myelin oligodendrocyte glycoprotein antibody-associated disease (MOGAD) in Korea, and to describe their relative proportions. METHODS: From January to March 2025, 47 referral hospitals participating in a nationwide hospital-based registry identified actively followed patients with MS, NMOSD, or MOGAD. Diagnoses followed international criteria, and antibody status was confirmed using validated CBAs. Actively followed patients had ≥1 outpatient visit in the prior 6 months. Centers provided demographics, treatments, and Expanded Disability Status Scale. Prevalence used national population data. RESULTS: A total of 4,196 patients were identified, 1,799 MS, 1,616 NMOSD, and 781 MOGAD (ratio 2.3:2.1:1). Mean age at onset was 33.4 ± 12.0 years for MS, 42.7 ± 14.7 for NMOSD, and 41.7 ± 17.8 for MOGAD, and the female-to-male ratios were 2.2:1 for MS, 5.1:1 for NMOSD (6.5:1 in aquaporin-4-IgG positive cases), and 1.5:1 for MOGAD. Crude prevalence estimates were 3.48, 3.13, and 1.51 per 100,000, respectively. DISCUSSION: This nationwide registry demonstrates a distinctive Korean CNS inflammatory demyelinating disease profile, with a relatively higher proportion of NMOSD and MOGAD reflecting the low prevalence of MS in East Asia.