Pediatric optic neuritis and anti MOG antibodies: a cohort of Italian patients

Background: recent studies reported that anti myelin oligodendrocyte glycoprotein (MOG) antibody (ab) related optic neuritis (ON) tend to have characteristics that differ from seronegative ones. The aim of our study was to investigate the clinical characteristics of pediatric anti-MOG ON by comparing anti MOG-ab-seropositive and seronegative patients with ON. Methods: in this retrospective Italian multicentre study, participants were identified by chart review of patients evaluated for acquired demyelinating syndromes of the central nervous system (over the period 2009-2019). We selected patients presenting with ON as their first demyelinating event. Inclusion criteria were age < 18 years at symptoms onset; presentation consistent with ON; negativity of anti-aquaporin 4 antibodies (AQP4). Only patients who were tested for MOG-IgG1-ab with a live cell-based assay were included. Results: 22 patients (10 MOG-ab-positive and 12 MOG-ab-negative) were included. Fundus oculi examination at onset showed disc swelling in 9/10 in the MOG-ab-positive cohort and 2/10 in the seronegative group (P = 0.002). Retinal Fiber Nerve Layer (RFNL) thickness measured by Spectral Domain Optical Coherence Tomography (S-OCT) was increased in the 5/5 MOG-ab-positive patients tested and was normal or reduced in the seronegative patients tested (4/4 patients) (P = 0.024). Visual acuity impairment at onset did not differ significantly between the two groups, but the MOG-ab-positive cohort showed better recovery at follow-up both regarding visual acuity (P= 0.025) and expanded disability status scale (EDSS) (P= 0.013). A final diagnosis of MS was frequent among seronegative patients (6/12, 50%), whereas none of the MOG-ab-positive group received a diagnosis of MS (P = 0.015). Clinical relapse frequency was low in both groups: 2/10 MOG-ab-positive and 2/12 seronegative cases relapsed, with a median follow up of 25 months. Conclusion: optic disc swelling and increased RFNL at baseline are strongly associated with MOG-ab positivity. MOG-ab-positive patients with ON showed better recovery compared to the seronegative ones. The relapse rate was low and did not differ among the two groups.