A recent retrospective study found that serum biomarkers, including glial fibrillary acidic protein, tau, and ubiquitin C-terminal hydrolase L1, distinguish between double seronegative and aquaporin-4 antibody-positive neuromyelitis optica spectrum disorder, which is indicative of the heterogeneous nature of the former condition. Neuromyelitis optica spectrum disorder (NMOSD) is characterized by recurrent optic neuritis with or without...