MOG and myelitis: All MOG-IgG-positive patients in group I had a history of ON and/or myelitis (Table 1, Fig. 3); 22/50 (44 %) had a history of both ON and myelitis; 22/50 (44 %) had a history of ON but not of myelitis (recurrent in 13); and 6/50 (12 %) had a history of longitudinally extensive myelitis (LETM) but not of ON.