MOG and erythema multiforme: For example, isolated uni- or bilateral optic neuritis has been reported as the most common symptom at MOG-EM disease onset (64% and 73% of patients in a German and an Australasian/New Zealand cohort of patients with MOG-EM) [8, 16] and isolated LETM was the first clinical symptom in only 11% and 18% of these patients.