This study aimed to evaluate the potential utility of glial fibrillary acidic protein (GFAP) and neurofilament light chain (NfL) as biomarkers of disease activity in AQP4-IgG-positive neuromyelitis optica spectrum disorder (NMOSD) and MOG antibody-associated disease (MOGAD). The gene discussed is AQP4; the disease is neuromyelitis optica.