Aquaporin 4 antibody-positive neuromyelitis optica spectrum disorders and myelin oligodendrocyte glycoprotein antibody-associated encephalomyelitis. A brief review

Aquaporin 4 (AQP4) immunoglobulin (Ig)G-associated neuromyelitis optica spectrum disorders (NMOSD) and myelin oligodendrocyte glycoprotein immunoglobulin (Ig)G-associated encephalomyelitis (MOG-EM, also termed MOG antibody-associated disease, MOGAD) are important autoimmune differential diagnoses of multiple sclerosis (MS), which differ from MS with respect to optimum treatment and prognosis. AQP4 IgG-positive NMOSD take a relapsing course in virtually all cases and MOG-EM in at least 80% of adult cases. Both diseases can quickly lead to permanent disability if left untreated, although MOG-EM is associated with a better overall long-term prognosis. Antibody testing must be carried out by means of so-called cell-based assays. A number of red flags have been defined that must be checked prior to making a diagnosis of NMOSD or MOG-EM. Acute attacks are treated using high-dose glucocorticoids and plasma exchange or immunoadsorption. Rituximab and other immunosuppressants are used off-label for attack prevention. Recently, eculizumab, a C5 complement inhibitor, has been approved in the European Union (EU) for the treatment of patients with AQP4 IgG-positive NMOSD. This article gives a brief overview of the clinical and paraclinical features, pathology, treatment and prognosis of these rare disorders.