Diagnosis and classification of neuromyelitis optica
Neuromyelitis optica (NMO), is an autoimmune disorder of the central
nervous system (CNS), mainly affecting the spinal cord and optic nerves.
NMO is more prevalent in women than men, with a female predominance
usually higher than observed in MS. The median age of onset is also
higher than MS, with a median of 35–45 years. Cases of NMO are more
prevalent in areas of non-Caucasian populations, especially in Asian
In 2004 Lennon et al. described a circulating IgG auto-antibody
(NMO-IgG) in patients with NMO, that was absent in those with multiple
sclerosis. This NMO-IgG target was identfied as the astrocyte water
channel protein aquaporin 4 (AQP4). Pathological changes attributed to
NMO occur mostly in the spinal cord and optic nerve, and to a lesser
extent in the brain. Pathogenesis occurs by complement-mediated
astrocyte damage, cascading to leukocyte infiltration, oligodendrocyte
death and neuronal cell damage. The result is necrosis of major CNS cell
types, explaining the poor recovery and major neurological deficits.
Revised diagnostic criteria for NMO of Wingerchuk et al in 2006 defined
definite NMO as consisting of optic neuritis and acute myelitis, with
two of three additionally supportive criteria, consisting of
longitudinally extensive spinal cord lesions, brain MRI not meeting the
diagnosis of MS and seropositive NMO. NMO-IgG seropositivity predicts
relapse and conversion to NMO in patients with recurrent optic neuritis
and a single attack of longitudinally extensive transverse myelitis.
Reports show that seropositive NMO differs from seronegative disease
both clinically and epidemiologically, reflecting strong predominance in
women, frequent association with other autoimmune disorders, more
frequent and severe attacks and higher spinal cord lesion load. Whether
seronegative disease represents optico-spinal MS or reflects pathogenic
diversity in NMO, such as seronegative myasthenia gravis, is still
Authors: Drori T, Chapman J
Source: Autoimmun Rev. 2014 Apr-May;13(4-5):531-3. doi: 10.1016/j.autrev.2014.01.034. Epub 2014 Jan 11.
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