Optic neuritis (ON) describes an inflammation of the optic nerve that is a common manifestation of demyelinating autoimmune diseases such as multiple sclerosis (MS), aquaporin‐4‐IgG positive (AQP4‐IgG+) and seronegative neuromyelitis optica spectrum disorder (NMOSD) and myelin oligodendrocyte glycoprotein (MOG) antibody‐associated diseases (MOGAD).1, 2 Worldwide incidence of ON is between 1 and 3 per 100.000 person per year.3 The gene discussed is AQP4; the disease is optic neuritis.