Neuromyelitis Optica spectrum disorder (NMOSD) is an autoimmune inflammatory disorder that affects the central nervous system (CNS) and causes a range of symptoms, most commonly optic neuritis and transverse myelitis (Jarius et al., 2020). Historically, NMOSD was considered a subtype of multiple sclerosis (MS); however, with the discovery of the disease-specific immunoglobulin G (IgG) autoantibodies binding to astrocyte water channel aquaporin 4 (AQP4) in the CNS, it is now classified as a distinct entity (Fujihara et al., 2012).

The prevalence of NMOSD varies worldwide, with estimates ranging from 1 per 100,000 among white populations to 10 per 100,000 among black populations (Hor et al., 2020). Several studies have reported an increase in the prevalence of NMOSD globally (Bagherieh et al., 2023), which may partly be explained by improved diagnostic criteria (Carnero Contentti and Correale, 2021; Wingerchuk et al., 2015). In Tehran, the capital city of Iran, the prevalence of NMOSD has increased from 0.86 per 100,000 population in 2016 (Eskandarieh et al., 2017) to 1.31 per 100,000 in 2019 (Rezaeimanesh et al., 2020). Despite the significant burden of the disease, there is insufficient data on the prevalence and patterns of care for NMOSD in Iran (Rezaeimanesh et al., 2020; Shabany et al., 2021).

Chronic disease registries can provide valuable data through longitudinal monitoring and systematic collection, which is essential for developing optimal treatment strategies (Solomon et al., 2017). Such systems can serve as a valuable resource for tracking the distribution of the disease and evaluating the effectiveness of treatments. Therefore, the establishment of an accurate and comprehensive database is of great clinical importance (Ayoubi et al., 2023). There are several NMOSD registries around the world including the MSBase of Australia (Kunchok et al., 2020), Argentina (Rojas et al., 2020), France (Demuth et al., 2022) China (Huang et al., 2022) and Portugal (Santos et al., 2021).

As disability in NMOSD is attack-related, follow-up of patients is critical adding to the importance of the registry. This study aimed to establish a NMOSD data set for the national registry system in Iran (NMORI) and assess the validity of the developed data set.