Paediatric onset inflammatory bowel disease is a distinct and aggressive phenotype - a comparative population-based study

Summary Background: Paediatric onset IBD (pIBD) has been reported to be more aggressive than adult onset IBD (aIBD). Yet, a more extensive disease presentation in paediatric onset ulcerative colitis (pUC) has been the only consistent finding. Aims: In a population‐based study, we aimed to further elucidate the differences in disease course between pIBD and aIBD. Methods: We compared a pIBD cohort (diagnosis <15 years of age) and an aIBD cohort (diagnosis ≥18 years of age). Medical records were retrieved manually at last follow‐up, and clinical data concerning IBD phenotype and treatment were registered. Results: We included 333 pIBD and 449 aIBD patients. Patients with pIBD more often presented with extensive disease localisation than aIBD (24%/9% of pCD/aCD with L4 disease localisation and 67%/24% of pUC/aUC with E3 disease extent). Of the patients with inflammatory disease at diagnosis, 34% and 16% of pCD and aCD patients, respectively, progressed to complicated disease over the first 7 years after diagnosis (P = .002). Patients with pUC were more often treated with systemic corticosteroids (HR: 2.0 [CI: 1.6‐2.6], P < .0001) and/or thiopurines (HR: 3.8 [CI: 2.8‐5.2], P < .0001). Lastly, pIBD patients more often received biologics (HR: 2.5 [CI: 1.8‐3.6, P < .0001] in CD and HR: 3.8 [CI: 2.1‐6.9, P < .0001] in UC) and had an increased risk of relapse (incidence rate ratio of 1.8 [CI: 1.4‐2.2, P < .0001]). Conclusions: In this population‐based cohort study we demonstrated a more severe disease course in pIBD than in aIBD. This message should be considered by both paediatric and adult gastroenterologists when caring for pIBD patients.