Regional Trends and Patterns of Axial Spondyloarthritis in Latin America: A Study from the ESPALDA Registry (2019–2024)

Objective To compare demographic, clinical, functional, and therapeutic characteristics of patients with axial spondyloarthritis (axSpA) across three Latin American regions using data from the ESPALDA registry between January 2019 and December 2024. Methods This cross-sectional study included 418 patients diagnosed with axSpA who fulfilled ASAS classification criteria. Participants were recruited from three regions: Northern (Mexico), Andean (Colombia, Ecuador, Peru, Venezuela), and Southern (Argentina, Chile, Paraguay, Uruguay). Collected data included demographic features, HLA-B27 status, extra-articular manifestations, disease activity, radiographic damage, and treatments. Results The Northern region showed the highest prevalence of HLA-B27 (81%) and uveitis (36.3%), along with lower frequencies of peripheral involvement and fewer patients with MRI sacroiliitis (12.9%) (all p ≤ 0.003). In contrast, the Southern region reported a later onset of inflammatory back pain (median 39 vs. 22 years; p = 0.01), higher BASFI scores (median 4.6 vs. 2.87; p = 0.004), and a lower response to NSAIDs (59.8% vs. >77%; p = 0.001). Use of biologic DMARDs was lowest in the Northern region (34.4%) compared with the Andean (58.2%) and Southern (53.9%) regions (p ≤ 0.002 for North vs. others). The median diagnostic delay was 40.9 months (IQR 21–120), with no significant regional differences. Conclusion Two clinical phenotypes of axSpA appear to exist in Latin America: a predominantly axial, HLA-B27–positive phenotype in the Northern region, and a second phenotype in the Andean and Southern regions characterized by greater peripheral involvement and, in the South, later symptom onset and worse functional status.