Persistent MOG-IgG positivity is a predictor of recurrence in MOG-IgG-associated optic neuritis, encephalitis and myelitis.

Background: MOG-IgG-associated optic neuritis, encephalitis and myelitis (MONEM) is a recently recognized group of inflammatory central nervous system (CNS) disorders distinct from multiple sclerosis and neuromyelitis optica spectrum disorders. Limited data are available regarding the predictors of relapse in this condition.

Objective: We aimed to evaluate the longitudinal serostatus of patients with MOG-IgG and to correlate serostatus with long-term clinical outcomes.

Methods: Of 574 consecutive patients who presented with demyelinating inflammatory CNS disorders, we included 31 patients who were MOG-IgG-positive. Patients with MOG-IgG were followed up from 2011 to 2017 at the School of Medicine, University of São Paulo, Brazil.

Results: Relapsing disease occurred in 23 out of 31 patients (74%), while 8 (26%) exhibited a monophasic course. All monophasic patients, as well as the majority of relapsing patients, became seronegative during clinical remission. Patients exhibiting disease activity in the last 2 years were more likely to remain positive, with higher medium titres than those found in patients in clinical remission.

Conclusion: MOG-IgG patients usually present with a relapsing course, and the risk of relapse was associated with longitudinally persistent MOG-IgG seropositivity. In contrast, patients who experienced a single attack became spontaneously seronegative for MOG-IgG during long-term follow-up.