Comparative analysis of AQP4-IgG-positive and AQP4-IgG-negative NMOSD: A multicenter study in Latin America

Background: NMOSD is a rare autoimmune disorder with variable clinical presentations depending on AQP4-IgG serostatus. While AQP4-IgG-positive NMOSD is well described, data on seronegative cases, especially in Latin America, remain limited. Objective: To characterize the demographic and clinical features of NMOSD in Latin America, comparing AQP4-IgG-positive and AQP4-IgG-negative cases. Methods: A retrospective multicenter cohort study was conducted across Latin American NMOSD-specialized centers. Patients meeting the 2015-IPND diagnostic criteria were included. Results: Of the of 875 patients, 791 were included: 613 AQP4-IgG-positive and 178 AQP4-IgG-negative. AQP4-IgG-positive patients were more often female (87.4 % vs. 81.5 %, p = 0.05) and had a higher age at onset (41.4 vs. 38.0 years, p < 0.01). They more frequently presented with unilateral optic neuritis (30.1 % vs. 20.2 %, p < 0.01) and area postrema syndrome (9.3 % vs. 3.9 %, p < 0.01). Median EDSS at diagnosis was higher in the seronegative group (4.2 vs. 3.9, p < 0.01). Diagnostic delay was longer in this group as well, though not statistically significant. Older age at onset was the only independent predictor of AQP4-IgG positivity (OR = 1.02, p = 0.028). Conclusions: AQP4-IgG-positive and seronegative NMOSD differ in clinical and demographic features, underscoring the need for tailored diagnostic and therapeutic approaches.