To assess the frequency of MOG-IgA seropositivity, we investigated MOG-IgA, MOG-IgG, and MOG-IgM in 1339 patients with CNS demyelination (MS, n = 865; NMOSD, n = 196; other demyelinating diseases, n = 278) (Figure 1A-C). Here, MOG is linked to demyelinating disease.