AQP4 and neuromyelitis optica: Myelin oligodendrocyte glycoprotein (MOG) antibody-associated disease (MOGAD) overlaps with multiple sclerosis, acute disseminated encephalomyelitis, and aquaporin 4 antibody (AQP4-Ab)-positive neuromyelitis optica spectrum disorders (NMOSD) in terms of clinical phenotype, and is now considered to be a new and independent entity in inflammatory demyelinating diseases of the central nervous system (Ramanathan et al., 2016; Cobo-Calvo et al., 2019).