Children and Adolescents Diagnosed With Inflammatory Bowel Disease Are at Increased Risk of Developing Diseases With a Possible Autoimmune Pathogenesis

Background The development of diseases with a possible autoimmune pathogenesis is common in adults with inflammatory bowel disease (IBD). In early onset IBD, it may differ but the evidence is sparse. We aimed to investigate the risk and time span from IBD diagnosis to outcomes with different associated disorders with possible autoimmune pathogenesis.Methods A register-based study included all Danish patients with early onset of IBD (<= 18 years) between 1980 and 2021 and 50 matched references without IBD for each case. We examined the risk of type 1 and type 2 diabetes, celiac disease, thyroid disease, rheumatoid arthritis, psoriatic arthritis, and spondyloarthritis in Cox regression models.Results In total, 6822 patients with IBD were identified, and 337 728 matched references. The median age at the time of IBD diagnosis or index date for the matched references was 16 years (25-75 percentile: 13-18 years), and the median age at the time of an outcome or at the end of follow-up was 28.1 years (25-75 percentile: 21.5-37.0 years). According to the cumulative incidence plots psoriatic arthritis, and spondyloarthritis was diagnosed approximately 10 years after the IBD onset, and the remaining outcomes later. The adjusted hazard ratio after full follow-up was 4.72 (95% CI, 3.85-5.80) for psoriatic arthritis, 5.21 (95% CI, 4.17-6.50) for spondyloarthritis, 2.77 (95% CI, 1.92-4.00) for celiac disease, 2.15 (95% CI, 1.54-3.01) for rheumatoid arthritis, 1.69 (95% CI, 1.23-2.32) and 1.64 (95% CI, 1.21-2.21) for type 1 and type 2 diabetes, respectively. For thyroid disease, it was 1.16 (95% CI, 0.97-1.40).Conclusions The risk estimates were significantly increased for all outcomes at the end of follow-up, except for thyroid disease, but according to the cumulative incidence plots, only psoriatic arthritis and spondyloarthritis occurred earlier in the IBD cohort than in the matched references. Children and adolescents diagnosed with inflammatory bowel disease are at increased risk of developing several diseases with possible autoimmune pathogenesis compared with a matched reference group. Cumulative incidence curves showed that psoriatic arthritis and spondyloarthritis debut in young adulthood when compared with a matched reference group without IBD. Graphical Abstract