Still’s Disease Across Ages

Still’s disease has long been divided by age at onset into systemic juvenile idiopathic arthritis (sJIA) and adult-onset Still’s disease (AOSD). The 2024 evidence synthesis prepared for the European Alliance of Associations for Rheumatology/Pediatric Rheumatology European Society (EULAR/PReS) recommendations concluded that available systematic reviews and meta-analyses support the concept that sJIA and AOSD are the same disease expressed across different ages, rather than two distinct entities. Both sJIA and AOSD are dominated by systemic inflammation characterized by fever, rash, arthritis, marked acute-phase response, hyperferritinemia, and risk of macrophage activation syndrome. Most clinical manifestations occur at broadly similar frequencies in pediatric and adult disease, with myalgia, sore throat, and weight loss being more commonly observed in AOSD, while arthritis appeared more frequently in sJIA. Leukocytosis and extraarticular organ involvement were more commonly reported in AOSD. At the mechanistic level, the strongest unifying concept is dysregulated innate immunity, with IL-1, IL-6, and IL-18 pathways repeatedly identified as central to disease expression in both populations. The EULAR/PreS recommendations state that IL-1 or IL-6 inhibition should be initiated as early as possible once the diagnosis is established, reflecting a modern shift away from prolonged glucocorticoid-centered management. The 2026 systematic review of worldwide cohorts adds another important practical message: clinical features and outcome measures remain inconsistently collected across age groups, strengthening the need for a unified minimal dataset if sJIA and AOSD are truly approached as one disease. While age at onset may influence disease expression, it does not obscure the fundamental similarities in inflammatory pathways, clinical spectrum, complications, and therapeutic responsiveness. Viewing Still’s disease through a lifespan perspective may enable earlier diagnosis, encourage more timely targeted treatment, and establish a more unified framework for clinical care and future research.