Frequency of anti-MOG antibodies in serum and CSF of patients with possible autoimmune encephalitis: Results from a Brazilian multicentric study

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IntroductionMOGAD encephalitis and ADEM share several clinical features with autoimmune encephalitis (AE) associated with antineuronal antibodies (ANeA); nonetheless, treatment and prognosis differ. Anti-MOG antibodies (abs) are not routinely tested in possible AE, and epidemiological studies on MOGAD encephalitis are scarce. ObjectivesTo determine the frequency of anti-MOG abs in the serum and CSF in a cohort of possible AE and to compare the clinical characteristics of MOGAD patients and those with seropositive AE. Methods481 patients with possible AE from the Brazilian Autoimmune Encephalitis Network underwent tissue-based assay and cell-based assay (CBA) for ANeA. Anti-MOG abs were assessed in serum and CSF with in-house CBA. Clinical and laboratory characteristics of MOGAD and seropositive AE patients were compared. ResultsOf the 481 patients, 87 (18 %) had ANeA, and 17 (3.5 %) had anti-MOG abs. Three AE patients with anti-MOG abs and ANeA were excluded from further analysis. Anti-MOG abs were detected in 4 (1.2 %) of the 328 adults and 10 (6.5 %) of the 153 children. Of the 14 patients with MOGAD, nine had ADEM (mostly children), and five had encephalitis (including three adults). Only one patient with ADEM had anti-MOG abs exclusively in CSF. All patients with MOGAD encephalitis were seropositive for anti-MOG abs, and three had normal brain MRI. Patients with MOGAD had fewer behavioral changes (MOGAD 21 % x AE 96 %, p ≤ 0.0001) and movement disorders (MOGAD 42 % x AE 81 %, p = 0.0017) and more demyelinating symptoms, such as myelitis and optic neuritis (MOGAD 14 % x AE 0 %, p = 0.013). ConclusionApproximately 3.5 % of patients with possible AE harbor anti-MOG abs, and 0.9 % of the adults had MOGAD encephalitis. Anti-MOG abs were more frequent than other ANeAs regularly tested in AE. We provide evidence that MOGAD is a differential diagnosis in possible AE, even in adult patients with normal brain MRI, and that serum anti-MOG should be considered as an add-on diagnostic tool in AE among adults and pediatric patients.