Within the NMO spectrum, the MOG antibody is positive in up to 42% of AQP4-seronegative cases.6 MOG is a minor myelin component that is expressed exclusively in the central nervous system on the surface of myelin and oligodendrocyte processes. The role of this glycoprotein is not well understood but is hypothesized to function as a cell surface receptor or cell adhesion molecule.7
Among a cohort of 252 patients from the United Kingdom who tested positive for the MOG-IgG1 antibody, optic neuritis was seen in 55%, while 18% experienced transverse myelitis, and 15% had a history of area postrema syndrome. A brain MRI identified lesions in all areas of the brain including the brain stem, cerebellum, and cerebral hemispheres.8
Risk factors for NMOSD include female gender, Asian and African ethnicities, Epstein Barr virus seropositivity, and tobacco abuse.
Differential diagnosis. Many diseases or conditions that are inflammatory, autoimmune, infectious, or neoplastic can involve the central nervous system and mimic the clinical and radiologic phenotypes of NMOSD-AQP4. They include lupus, SjÖgren’s syndrome, multiple sclerosis, sarcoidosis, acute disseminated encephalomyelitis, HIV, and vitamin B12 deficiency.
Treatment. The standard treatment is intravenous methylprednisolone, 1 g/d for 3 to 5 days followed by a steroid taper. Therapeutic plasma exchange is recommended for refractory cases and in patients with spinal cord demyelination.9-11 Rituximab is the first-line therapy for attack prevention12-15 in NMOSD broadly and may be effective in MOG antibody disease, as well. In an open-label study of patients with NMOSD treated with rituximab, 64% were relapse free at follow-up, which ranged from 12 to 67 months.13 In a long-term study of patients treated with rituximab, 87% maintained a reduced relapse rate and 93% had improvement or stability over a 5-year follow-up.14
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