AQP4 and myeloid sarcoma: The discovery of highly specific auto-antibodies against aquaporin-4 (AQP4) in 2005 has characterized NMOSD as new disease entity distinct from multiple sclerosis (MS) [2, 3] Although NMOSD occurs all over the world, a predilection for non-Caucasians has been proposed, especially observed in Asian countries [4].