Indeed, PLEX and rituximab are standard treatments both in patients with MOG-EM/MOGAD and in patients with syndromes considered to pose a high risk of MOG-EM/MOGAD, such as “neuromyelitis optica spectrum disorders without AQP4-IgG” [8, 33] or chronic relapsing inflammatory optic neuropathy (CRION), meaning that serological testing may be influenced by those treatments in many patients. This evidence concerns the gene AQP4 and neuromyelitis optica.