Prevalence of autoimmune diseases and other associated conditions in children and young adults with juvenile idiopathic arthritis

Objective Many autoimmune diseases share common pathogenic mechanisms; however, there are limited studies quantifying the coexistence of autoimmune diseases and associated conditions in patients with juvenile idiopathic arthritis (JIA). This large US-based study estimated and compared the prevalence of multiple coexisting autoimmune diseases in patients with JIA with a general paediatric (GP) patient population.Methods This retrospective cohort study was conducted using registry data from the Cincinnati Children’s Hospital Medical Center (January 2010–October 2018). The prevalence of multiple autoimmune diseases was estimated in patients (age <21 years) with JIA and a control group from the GP patient population. Crude prevalences of 26 prespecified autoimmune diseases and associated conditions were compared using Bayesian Poisson regression modelling for each year up to the end of the study period.Results Overall, 2026 patients were included in the JIA cohort and 41 572 in the GP cohort. Of 26 autoimmune diseases and associated conditions evaluated, 14 (53.8%) had a significantly higher prevalence in the JIA cohort compared with the GP cohort. In total, seven (26.9%) autoimmune diseases or associated conditions had a >20-fold increased prevalence in the JIA cohort compared with the GP cohort.Conclusion In this study, patients with JIA had a greater prevalence of a large number of coexisting autoimmune diseases and associated conditions compared with the GP population. Physicians should consider coexisting autoimmune diseases in the treatment and management of patients with JIA