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

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.