According to the IPND-2015 diagnostic criteria, AQP4-IgG should be tested in the serum of patients presenting with clinical features typical for NMOSD, such as extensive myelitis, recurrent myelitis, area postrema syndrome, or severe ON.1, 22, 28There is no recommendation for testing AQP4-IgG in CSF on a clinical basis. This evidence concerns the gene AQP4 and myelitis.