AQP4 and autoimmune disorder of central nervous system: Recent discovery of several autoantibodies, such as aquaporin-4 immunoglobulin G antibodies (AQP4-IgG), myelin oligodendrocyte glycoprotein immunoglobulin G antibodies (MOG-IgG) and glial fibrillary acidic protein immunoglobulin G antibodies (GFAP-IgG), has greatly facilitated differential diagnosis of autoimmune disorders of the central nervous system.