Background and AimsAcute optic neuritis (ON) is an inflammatory condition affecting the optic nerve. Clinicians should suspect optic neuritis in cases of painful and rapidly progressive loss of central visual field. This condi-tion may be associated with a multitude of diseases, and mostly with multiple sclerosis (MS) where may present as an initial symptom. The literature reports that optic neuritis and MS occur in patients with inflammatory bowel disease (IBD) before and after the era of anti-tumor necrosis factor-α (TNF-α) drugs. At the present moment, there is little consensus for managing this complication, currently treated with corticosteroids and discontinuation of the causative agents.MethodsWe collected cases through a retrospective multicenter European Crohn's and Colitis Organization CONFER (Collaborative Network For Exceptionally Rare case reports) project. We also performed a comprehensive retrospective search of the available litterature on this topic.ResultWe report herein 12 new cases of ON, including 10 under anti-TNF therapy, collected through the CONFER project. We also compare characteristics of ON associated with or without anti-TNF-α agents.ConclusionsThe exceptional and current observation of distant family history of MS in 17% of our patients who developed ON, despite the small number and the lack of a control arm, might be an important signal that should be taken into account in in our therapeutic strategies in the future.