AQP4 and multiple sclerosis: Myelin oligodendrocyte glycoprotein immunoglobulin G1 (MOG-IgG1)-associated disease is suggested as a separate disease entity distinct from multiple sclerosis and neuromyelitis optica spectrum disorder (NMOSD) with anti-aquaporin-4 IgG (AQP4-IgG); it has a predilection for the optic nerve rather than spinal cord, perineural enhancement extending to adjacent soft tissues on magnetic resonance imaging (MRI), and a less unfavorable prognosis than NMOSD [1].