Epidemiological findings of neuromyelitis optica spectrum disorders in a Venezuelan study

•The paper presents a cohort of patients with a confirmed diagnosis of NMOSD in Venezuela, from 2011 to 2018.•The prevalence of neuromyelitis optica spectrum disorders in Venezuela was 2.11 per 100,000.•The relative frequency (RF) of NMOSD is 23%, one of the highest in the region•This Venezuelan study on NMOSD also show a female predominance affecting mainly young patients•Our study provides a foundation for future epidemiological studies Neuromyelitis optica spectrum disorders (NMOSD), is a rare autoimmune inflammatory disease of the central nervous system. Since the countries of Latin America (LATAM) show contrast in geographic, social, environmental factors, and genetic heterogeneity, the information about NMOSD epidemiology in the region allows a better understanding of the disease and its clinical outcome. To determine the prevalence, relative frequency (RF), and clinical characteristics of NMOSD in a multiethnic Venezuelan cohort of patients with demyelinating disorders. We conducted a retrospective descriptive multicenter study of hospital case records of individuals with an established diagnosis of MS and NMOSD in the National Program for Multiple sclerosis (MS) from 2011 to 2018. We selected those NMOSD cases based on the 2006 Wingerchuck and the 2015 International panel for the diagnosis of Neuromyelitis optica (IPND) criteria. We identified 249 patients with NMOSD. The prevalence was 2.11 per100,000 individuals (95% confidence interval (CI)1.85 2.37), the RF was 23%, and the MS/NMOSD ratio was 3.2:1. The average disease onset occurred by the fourth decade of life (34±14.8 years of age); with a strong female predominance (female to male ratio: 4:1). Mestizos constituted 86,7% of this cohort. Most of the patients presented initially with simultaneous optic neuritis (ON) and acute transverse myelitis (ATM) and a recurrent course was registered in 82.3% of cases. The mean of the expanded disability status scale (EDSS) was 3.5 (IQR 2-7). Abnormal brain and spine MRI were present in 47.8% and 81.1% of patients, respectively. Antibodies against aquaporin-4 (AQP4) which were measured through a cell-based assay were positive in 55.3% of the individuals tested. The most used immunosuppressant agent was Azathioprine (57.4%). NMOSD in Venezuela affects mainly young Mestizo women and shows one of the highest relative frequency in the region. Planning and developing healthcare programs for underserved populations as well as more comprehensive LATAM studies ar