AQP4 and neuromyelitis optica: Several studies indicate that autoantibodies are central to the pathogenesis of MS and related disorders.6,7 For a long time neuromyelitis optica (NMO) was considered a variant of MS.8Lennon et al., described a novel serum antibody (NMO-IgG) that bound specifically to aquaporin-4 expressed on astrocytes.