Neuromyelitis optica (NMO), an uncommon central nervous system (CNS) demyelinating disease, produces transverse myelitis and severe optic neuritis. IgG-NMO autoantibody, a specific immunoglobulin binding aquaporin-4 water channel protein, confirms that NMO is a different entity to multiple sclerosis. Parallel to cytokine down-regulations found in serum of relapsing-NMO (rNMO) patients, it has been reported that IgG-NMO may also confer a worse course of the disease in r-NMO Caribbean patients. In this study, we were interested in exploring the influence of IgG-NMO autoantibody on S100beta levels and clinical parameters from serum of r-NMO patients. Serum samples from 24 rNMO patients and 10 controls were evaluated. The reduction of S100beta observed in r-NMO patients was not significant compared to controls; and no differences were present regarding IgG-NMO immunoreactivity. At the same time, a significant correlation was also observed between IgG-NMO autoantibody serum detection and EDSS (Expanded Disability Status Scale) in rNMO. These results corroborate a differential regulation of IgG-NMO autoantibodies on the S100beta glial marker and on the disability present in rNMO patients.