Conformation-sensitive MOG-ab detected by cell-based assays are positive in some cases with inflammatory CNS diseases including optic neuritis, myelitis, acute disseminated encephalomyelitis (ADEM), aquaporin-4 (AQP4) antibody (AQP4-ab)-negative neuromyelitis optica spectrum disorder (NMOSD), brainstem encephalitis, and cerebral cortical encephalitis, which are now called as MOG-ab-associated disease (MOGAD) [4]. The gene discussed is AQP4; the disease is neuromyelitis optica.