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.