Clear Positive MOG Antibodies in Adults With Multiple Sclerosis Features: Diagnostic Challenges

Background and objectives: Distinguishing multiple sclerosis (MS) from myelin oligodendrocyte glycoprotein antibody-associated disease (MOGAD) can be challenging because of some shared clinical and radiologic features. We aimed to describe adults with clear positive serum MOG antibodies (MOG-Abs) presenting with MS features and rethink their nosological framework.

Methods

We conducted a retrospective longitudinal study within the French NOMADMUS cohort and included adults from 2015 to 2025 tested clear positive for MOG-Ab in the serum with at least 1 MS-suggestive feature: (1) biological (CSF-specific oligoclonal bands [OCBs] and/or kappa free light chain index [KFLCi] ≥5.7) or (2) radiologic (≥1 lesion among juxtacortical lesion, Dawson finger, or inferior temporal lobe lesion). All MRI scans were reviewed blindly by an expert neuroradiologist. Minimum clinical and radiologic follow-up was 6 months. We classified patients as (1) typical MS when fulfilling 2024 McDonald criteria, with OCB and/or KFLCi ≥5.7 and showing no MOGAD supporting features, or (2) equivocal in all other situations.