AQP4 and neuromyelitis optica: Neuromyelitis Optica Spectrum Disorders (NMOSD) and Myelin oligodendrocyte glycoprotein (MOG) antibody-associated disease (MOGAD) are autoimmune disorders affecting the central nervous system.1,2 The detection of specific antibodies, respectively against the water channel acquaporin-4 (AQP4) and MOG, is critical for diagnosis, but the role of anti-AQP4 and -MOG antibody titres in managing NMOSD and MOGAD remains unclear.3,4