![]() ![]() Cell-based assays can be carried out using live cells or fixed cells (chemically or physically “fixed” to preserve the shape and contents of the cell even though they are dead). Cell-based assays are optimal for detection of MOG-IgG and have high specificity (≈98%) but false positives occur more commonly than with AQP4-IgG, particularly with low positive results (titer 1:20, 1:40 on flow cytometric assay at Mayo Clinic) or when ordered in low probability situations. In contrast with AQP4-IgG seropositive NMOSD, males and females are equally affected, and major differences in race/ethnicity have not been described. Onset is typically in the third decade of life, with up to half of all cases occurring in children. Unlike MS, a secondary progressive course is not encountered. The disease can be monophasic in up to half of patients and the remainder follow a relapsing course. It can also account for some patients with the syndrome NMOSD who lack AQP4-IgG. The disease is associated most often with attacks of acute disseminated encephalomyelitis (ADEM), optic neuritis, transverse myelitis, cerebral cortical encephalitis, or combinations thereof. Using updated cell-based assays, the true spectrum of MOGAD has been elucidated and its distinction from MS has become clearer. In 2007, when using assays to detect antibodies to the MOG protein in its native conformational form, it was first recognized that MOG-IgG is a biomarker of a distinct CNS demyelinating disease. AQP4-IgG seronegative NMOSD cases are described and account for 20% of NMOSD but represent a heterogeneous group of disorders and will not be a major focus of this review. ![]() The latest generation of AQP4-IgG cell-based assays are highly specific (> 99%) for this diagnosis. Unlike MS, it is generally not associated with a secondary progressive course. The median age of disease onset is 35–37 years, but onset has been described in both young children and elderly patients. AQP4-IgG seropositive NMOSD affects females 5–10 times more frequently than males and has a higher prevalence in non-white populations. Other attack types include acute brainstem syndrome, symptomatic narcolepsy or acute diencephalic clinical syndrome, and symptomatic cerebral syndrome with NMOSD-typical brain lesions. AQP4-IgG seropositive NMOSD is characterized by three major attack types: (1) transverse myelitis (2) optic neuritis (3) area postrema syndrome (which can lead to intractable nausea, vomiting and hiccups from involvement of the brain’s vomiting center) (5). AQP4-IgG seropositive NMOSD is relapsing in 90% of cases and attacks are often severe with incomplete recovery and thus disability will accumulate with each attack, further highlighting the importance of attack-prevention treatments in these patients. This was the first serum biomarker of any CNS demyelinating disease. In 20, an antibody biomarker of NMOSD was discovered that targets aquaporin-4, a water channel on the cell surface of astrocytes. They are now recognized as distinct diseases with important treatment and prognostic differences from each other and from MS. Prior to the discovery of their antibody biomarkers, these diseases were initially often categorized as a subtype of MS. Randomized placebo-controlled trials are urgently needed in this area.Īquaporin-4-IgG seropositive neuromyelitis optica spectrum disorder (AQP4-IgG seropositive NMOSD) and myelin oligodendrocyte glycoprotein antibody (MOG-IgG)–associated disease (MOGAD) are acquired inflammatory demyelinating diseases of the central nervous system (CNS), distinct from multiple sclerosis (MS). Observational benefit has been suggested from oral immunosuppressants, intravenous immunoglobulin (IVIg), rituximab, and tocilizumab. There is a lack of any class 1 evidence for MOGAD preventative treatment. MOGAD is much more likely to be monophasic than AQP4-IgG seropositive NMOSD, and preventative therapy is usually reserved for those who have had a disease relapse. ![]() Rituximab, eculizumab, inebilizumab, and satralizumab all have class 1 evidence for use in AQP4-IgG seropositive NMOSD, and the latter three have been approved by the US Food and Drug Administration (FDA). AQP4-IgG seropositive NMOSD has a relapsing course in most cases, and preventative maintenance treatments should be started after the initial attack. Aquaporin-4 (AQP4)-IgG seropositive neuromyelitis optica spectrum disorders (AQP4-IgG seropositive NMOSD) and myelin oligodendrocyte glycoprotein (MOG)–IgG-associated disease (MOGAD) are inflammatory demyelinating disorders distinct from each other and from multiple sclerosis (MS).While anti-CD20 treatments can be used to treat MS and AQP4-IgG seropositive NMOSD, some MS medications are ineffective or could exacerbate AQP4-IgG seropositive NMOSD including beta-interferons, natalizumab, and fingolimod. ![]()
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