What are the genetic changes related to neuromyelitis optica ?
No genes associated with neuromyelitis optica have been identified. However, a small percentage of people with this condition have a family member who is also affected, which indicates that there may be one or more genetic changes that increase susceptibility. It is thought that the inheritance of this condition is complex and that many environmental and genetic factors are involved in the development of the condition.  The aquaporin-4 protein (AQP4), a normal protein in the body, plays a role in neuromyelitis optica. The aquaporin-4 protein is found in several body systems but is most abundant in tissues of the central nervous system. Approximately 70 percent of people with this disorder produce an immune protein called an antibody that attaches (binds) to the aquaporin-4 protein. Antibodies normally bind to specific foreign particles and germs, marking them for destruction, but the antibody in people with neuromyelitis optica attacks a normal human protein; this type of antibody is called an autoantibody. The autoantibody in this condition is called NMO-IgG or anti-AQP4.  The binding of the NMO-IgG autoantibody to the aquaporin-4 protein turns on (activates) the complement system, which is a group of immune system proteins that work together to destroy pathogens, trigger inflammation, and remove debris from cells and tissues. Complement activation leads to the inflammation of the optic nerve and spinal cord that is characteristic of neuromyelitis optica, resulting in the signs and symptoms of the condition.  The levels of the NMO-IgG autoantibody are high during episodes of neuromyelitis optica, and the levels decrease between episodes with treatment of the disorder. However, it is unclear what triggers episodes to begin or end.