Purpose: To describe the clinical, radiological, immunological and electrophysiological features of a myelin oligodendrocyte glycoprotein (MOG)-IgG positive girl with five prior episodes of idiopathic bilateral optic neuritis (ON). Observations: We report a Danish girl who has been followed by pediatricians and pediatric neurologists since the age of 10 with recurrent episodes of idiopathic bilateral ON. Since the age of 15 there has been no recurrence of ON, and the patient has been thoroughly investigated for Multiple Sclerosis (MS) several times, but with negative findings. At the age of 19 the patient was referred to the Clinic of Optic Neuritis where she was tested seropositive for antibodies against MOG (MOG- IgG) on a conventionally cell-based assay. Despite 5 previous episodes of ON, the latency and amplitude signals of pattern-reversal visual evoked potentials (pVEP) including multifocal VEP were detected within the normal range. Conclusion: The clinical implications of MOG- IgG are not yet clear, but in cases where the diagnosis of MS is less likely and where ON is the main symptom, testing for both IgG antibodies against AQP4 and MOG while having atypical optic neuropathies in mind is important. MOG-IgG positive patients may have a good prognosis with regards to visual function.