[A concept of neuromyelitis optica in Japan]

Neuromyelitis optica (NMO) is an inflammatory disease of the central nervous system characterized by relapses of optic neuritis and acute myelitis. The disease was referred to as the optic-spinal form of multiple sclerosis (OSMS) in Japan for a long period. A specific auto-antibody, NMO-IgG, was detected in the serum of NMO patients, and aquaporin-4 water channel protein was detected as its target antigen; aquaporin-4 water channel protein is localized at the end-feet of astrocytes. Because of the presence of this specific serum auto-antibody, most OSMS patients in Japan were found to exhibit a disease that was identical to NMO that affects individuals of the Western countries. Since the discovery of NMO-IgG, various clinical and histopathological features of this condition have been recognized; in addition the concept of NMO has been established in Japan as well as in many other countries.