The MOG-IgG positive NMO patients consisted of two AQP4-IgG seronegative patients (a two year old female child and a 56 year old male), both with a MOG-IgG titer of 1:2,560, and one patient (a 39 year old woman) who was double positive for both, MOG-IgG (titer 1:160) and AQP4-IgG (titer 1:1,280). Here, AQP4 is linked to neuromyelitis optica.