MOG-IgG-positive myelitis and ON showed a significant overlap with AQP4-IgG-positive NMOSD in clinical and radiological presentation, with more than 60 % patients with a history of both ON and myelitis meeting Wingerchuk’s 2006 criteria for NMO [28] and around a third of all patients fulfilling the revised 2015 criteria [29]. The gene discussed is AQP4; the disease is myelitis.