NMO spreads worldwide and poor prognosis is still a challenge.2 In addition to clinical, laboratory, immunological, and pathological characteristics which are mainly used to distinguish NMO from MS, a serum autoantibody termed NMO-immunoglobulin G (IgG), which targets the astrocytic water channel aquaporin-4 (AQP4), has recently been characterized for more differentiation. The gene discussed is AQP4; the disease is neuromyelitis optica.