Myelin oligodendrocyte glycoprotein (MOG), a protein exclusively expressed on the surface of oligodendrocytes and myelin sheaths in the central nervous system (CNS), is immunopathogenetically distinct from classic multiple sclerosis and AQP4-IgG-positive neuromyelitis optica spectrum disorders.[1] Antibodies against MOG can be associated with a spectrum of clinical phenotypes, such as optic neuritis, myelitis, aseptic meningitis, encephalitis, and acute disseminated encephalomyelitis. The gene discussed is MOG; the disease is optic neuritis.