AQP4 and myeloid sarcoma: MOG-IgA was positive in 3 of 50 patients (6%) with NMOSD, in 5 of 228 patients (2%) with other demyelinating diseases, and in 10 of 848 patients (1%) with MS who were double-seronegative for AQP4-/MOG-IgG (Figure 1D).