Therefore, great efforts should be made to improve the sensitivity of assays; Secondly, it could be the matter of diagnostic criteria [2]; Finally, some AQP4-IgG seronegative patients with clinical signs of NMO might have antibodies against others antigens in the astrocytes, similarly as in myasthenia gravis, where patients seronegative for anti-acetylocholine receptor antibodies produce anti-MuSK or anti-titin antibodies [9]. This evidence concerns the gene AQP4 and neuromyelitis optica.