Neuromyelitis optica (NMO) is a central nervous system disorder that primarily affects the eye nerves (optic neuritis) and the spinal cord (myelitis). NMO is also known as neuromyelitis optica spectrum disorder or Devic’s disease. It occurs when your body’s immune system reacts against its own cells in the central nervous system, mainly in the optic nerves and spinal cord, but sometimes in the brain.
The cause of neuromyelitis optica is usually unknown, although it may sometimes appear after an infection, or it may be associated with another autoimmune condition. Neuromyelitis optica is often misdiagnosed as multiple sclerosis (MS) or perceived as a type of MS, but NMO is a distinct condition.
Neuromyelitis optica may cause blindness in one or both eyes, weakness or paralysis in the legs or arms, painful spasms, loss of sensation, uncontrollable vomiting and hiccups, and bladder or bowel dysfunction from spinal cord damage. Children may experience confusion, seizures or coma with NMO. Neuromyelitis optica flare-ups may be reversible, but can be severe enough to cause permanent visual loss and problems with walking.
The cause of NMO is thought to be due to a specific attack on the aquaporin-4 (AQP4) water channel located within the optic nerves and spinal cord. Aquaporins (AQPs) are proteins that transport water across cell membranes. More than 70% of NMO and NMOSD patients test positive for an antibody biomarker in the blood called the NMO-IgG or anti-AQP4 antibody.