Anti-myelin oligodendrocyte glycoprotein (MOG) antibody, which is specifically detected using a cell-based assay (CBA), has been identified in various demyelinating diseases, including neuromyelitis optica spectrum disorders (NMOSD), acute idiopathic optic neuritis (ON), and pediatric multiphasic disseminated encephalomyelitis. Although its pathogenic role has not been established, antibody seropositive cases appear to share several characteristic features, such as a preferable response to steroid therapy and a good prognosis. Antibody detection at the onset of a demyelinating disease is important to predict the prognosis. Further analysis of the clinical features and investigation of the pathogenic roles of the antibody are required to establish the disease spectrum associated with the antibody. Although the associated diseases appear to have a relatively good prognosis, treatment recommendations are offered for patients with severe symptoms or frequent relapses.