The distinction between the more common Multiple Sclerosis (MS), which shares some clinical and radiological disease characteristics [3], and NMO depended solely on clinical features until the antibody against the astroglial surface protein aquaporin 4 (AQP4-IgG), highly specific for NMO, was discovered in 2004 [4, 5]. The gene discussed is AQP4; the disease is neuromyelitis optica.