Nevertheless, AQP4-IgG seronegativity in 10%–25% of NMO patients suggests that there are several other factors involved in NMO immunopathogenesis, i.e., autoantibodies against aquaporin-1 (AQP1-Abs) and antibodies against myelin oligodendrocyte glycoprotein (MOG-IgGs). Here, AQP1 is linked to neuromyelitis optica.