Neuromyelitis Optica Spectrum Disorder

OBJECTIVE: This article reviews the clinical features of and diagnostic and treatment approaches to neuromyelitis optica spectrum disorder (NMOSD), with additional focus on rare phenotypes and specific contexts. Pathogenesis and pathology, differential diagnoses, and the potential use of novel biomarkers are also discussed. LATEST DEVELOPMENTS: A major advancement in the characterization of NMOSD was the discovery of serum antibodies targeting the water channel aquaporin-4 in the majority of patients, which also improved the characterization of disease pathogenesis. A proper diagnosis is fundamental to differentiating NMOSD from other central nervous system inflammatory conditions and starting prompt treatment. The recent development of dedicated clinical trials led to the approval of new targeted drugs and further emphasized the relevance of properly recognizing this disease. The ongoing revision of NMOSD diagnostic criteria will provide additional guidance. ESSENTIAL POINTS: Although rare, recognizing NMOSD is crucial for improving patient outcomes through correct diagnostic and treatment approaches. Reports of atypical forms and increasing knowledge of clinical, imaging, and laboratory-specific features are fundamental for the accurate recognition of this condition. Research on targeted therapies and biomarkers measuring and predicting disease activity will improve NMOSD management.