AQP4 and optic neuritis: In the last decades, several studies reported that autoantibodies against the myelin oligodendrocyte glycoprotein (MOG) are associated with inflammatory demyelinating diseases of the central nervous system (CNS), such as acute disseminated encephalomyelitis (ADEM), monophasic or recurrent isolated optic neuritis (ON) or transverse myelitis (TM), pediatric multiple sclerosis (MS), aquaporin-4 (AQP4)-seronegative neuromyelitis optica spectrum disorders (NMOSD), and N-methyl d aspartate receptor (NMDAR) encephalitis with overlapping demyelinating syndromes [1–16].