Definition:

Neuromyelitis optica (NMO), also known as Devic's disease is an inflammatory demyelinating disease that selectively affects optic nerves and spinal cord. The etiology of NMO is unknown but it is believed to be an autoimmune disorder triggered by an environmental factor, possibly an infection, in genetically susceptible individuals. The principal effector in NMO is the self-reactive, complement-activating anti-AQP4 antibody. AQP4 water channel is a component of the dystroglycan protein complex located in astrocytic foot processes at the blood-brain barrier. Anti-AQP4 antibody is sensitive and highly specific serum markers of autoimmune NMO. For many decades, NMO was considered to be a subtype of multiple sclerosis (MS), but prognosis and optimal treatments differ. Corticosteroids and plasma exchange (PLEX) are the most commonly used therapeutic modalities in acute settings. Corticosteroids exert global immunosuppressive and anti-inflammatory effects, whereas PLEX removes antibodies, complement, and cytokines from the blood. Besides, immunosuppressant agents interfering with the function of T and B cells have been shown to prevent disease relapses and reduce neurological disability in NMO.