Myelin oligodendrocyte glycoprotein-positive optic neuritis masquerading as pseudotumor cerebri at presentation.

Optic neuritis (ON) is a common clinical manifestation in myelin oligodendrocyte glycoprotein (MOG) antibody-associated disease. Other clinical manifestations include acute demyelinating encephalomyelitis, transverse myelitis and neuromyelitis optica spectrum disorders. Uncommon presentations of MOG-positive disease have recently been reported. ON in MOG-positive disease commonly involves the anterior portion of both optic nerves, leading to bilateral disc swelling. During the early stages of ON, in the setting of bilateral disc swelling and pain, patients may initially be suspected as pseudotumor cerebri (PTC). In this study, we report five cases presenting early in the course of MOG-IgG-related ON, which were misdiagnosed as PTC in the emergency department. MOG-IgG-positive ON requires timely treatment to prevent RNFL and vision loss secondary to the high relapse rate associated with these antibodies. Our aim is to increase the awareness of the unique findings of MOG-IgG-positive ON, which may initially mimic PTC, thereby delaying treatment.