MOG- encephalitis is the most prevalent autoimmune encephalitis in children.

Background: Encephalitis in children is a serious inflammatory brain disease caused by infectious or autoimmune-mediated processes. The frequency of auto-immune variants in pediatric populations is not entirely clear.

Objective: To study the frequency of myelin oligodendrocyte glycoprotein (MOG) anti-body (ab)-mediated autoimmune encephalitis (AE) in children included in the Men-ingitis/Encephalitis register of Lower Saxony (MERIN).

Methods: Medical records of 1341 children treated between 2011 and 2020 in two large children's hospitals participating in a prospective study on encephalitis (ME-RIN) were reviewed. Children meeting diagnostic criteria for possible AE were fi-nally included if serum samples and informed re-consent were available. Children with a pathogen-mediated encephalitis were also included as controls. All availa-ble serum samples were tested for MOG- and anti-N-methyl-D-aspartate receptor (NMDAR) antibodies (abs) using cell- and tissue-based assay (TBA).

Results: We included 55 children of whom 16 had pathogen-associated menin-goencephalitis. 39/55 children were classified as possible AE and 3/39 fulfilled the criteria for MOG ab-associated disease (MOGAD). No patients' sera harbored NMDAR abs. However, 5/39 patients fulfilled criteria for probable, auto-ab-negative AE.

Conclusions: In line with recent research our study suggests that ab-mediated AE and probable ab-negative AE are rare in children. The existing criteria seem suita-ble for identifying patients with AE but should include the testing of serum MOG abs. Further yet unknown abs may play a role in children with AE.