The inflammatory autoimmune disease neuromyelitis optica (NMO, opticospinal encephalomyelitis, Devic's syndrome) is a rare form (around 1%) of the group of acquired demyelinating diseases of the central nervous system (CNS) with degradation of the insulating sheath of at least one optical nerve (neuritis nervi optici) and at the same time of a few months later the spinal cord (myelitis). Diagnosis is made mostly clinically with anamnesis, neurological and neurophysiological tests, MRT of the CNS and lumbar puncture. The diagnosis NMO is confirmed in laboratory diagnostics by the determination of autoantibodies against AQP-4. The major significance of the autoantibody detection is that autoantibodies against AQP-4 (NMO-IgG) allow serological differentiation of prognostically poor NMO from classic multiple sclerosis (MS), which can influence therapy decisions significantly. While MS is treated with immune-modulating substances, NMO requires the use of immuno-suppressive drugs.

Autoantibodies against AQP-4 are highly specific serum autoantibody markers which are found very frequently in NMO, while they are not detected in multiple sclerosis (MS) patients or in healthy subjects. AQP-4 IgG may be associated with other autoantibodies, such as those against the cell nucleus (ANA), SS-A (Ro) or thyroperoxidase (TPO). This suggests that NMO can occur together with autoimmun diseases such as systemic lupus erythematosus (SLE), Sjogren's Syndrome, etc. A diagnosis should not be made based on a single test result. The clinical symptoms of the patient should always be taken into account along with the serological results by the physician.