[Neuromyelitis optica: the disease entity, pathogenesis and therapy].

Neuromyelitis optica (NMO) is clinically characterized by severe optic neuritis and transverse myelitis. Recurrent NMO has been described as optic-spinal multiple sclerosis (OSMS) in Japan, but it has been known that NMO has distinct clinical and laboratory findings (female preponderance, severe disability, longitudinally extensive myelitis, CSF-pleocytosis, negative oligoclonal IgG bands, etc) from those in typical MS. In addition, anti-aquaporin-4 (AQP4) antibody and loss of AQP4 in the active perivascular NMO lesions with deposition of immunoglobulins and activated complements were recently found to be NMO-specific, strongly suggesting that NMO is a clinical entity that should be separated from MS. In accordance with these unique features of NMO, different therapeutic responses between NMO and MS have been observed, that is, interferon-beta, a disease-modifying therapy (DMT) for MS, is less effective in NMO, while long-term administration of corticosteroid and immunosuppressive agents reduce relapses of NMO. Efficacy of plasma exchange for acute exacerbation in NMO supports the pathogenetic importance of humoral immunity in the disease. Meanwhile, in clinical practice, it is important to differentiate "genuine OSMS" characterized by short spinal cord lesions and anti-AQP4 antibody-negative status from NMO, because such cases with "genuine OSMS" are expected to respond to DMT for MS.