BACKGROUND AND AIMS The long-term outcomes of paediatric-onset inflammatory bowel disease [pIBD] in non-Caucasian populations are unknown. We therefore evaluated and compared the clinical features and long-term outcomes of pIBD with those of adult-onset IBD [aIBD] using a population-based cohort in the Songpa-Kangdong district of Seoul, Korea.

METHODS Clinical characteristics and prognoses were compared between the two groups: pIBD [defined as <18 years of age at diagnosis] and aIBD [18-59 years of age at diagnosis].

RESULTS We identified 131 patients with pIBD (48 ulcerative colitis [UC], 83 Crohn's disease [CD]) and 1192 patients with aIBD [866 UC, 326 CD] during 1986-2015. Extensive colitis at diagnosis was more prevalent in pUC than in aUC [45.8% vs 22.3%, p < 0.001], and the overall exposure to corticosteroids, thiopurines and anti-tumour necrosis factor agents was higher in pUC than in aUC [p < 0.001]. The cumulative risk of colectomy was higher in pUC than in aUC during a median follow-up of 125.0 and 112.1 months, respectively [8.9% vs 1.8% at 10 years after diagnosis, p = 0.030]. Ileocolonic location and inflammatory behaviour at diagnosis were more common in pCD than in aCD; however, patients with pCD and aCD did not differ regarding treatment or disease course during a median follow-up of 137.2 and 120.9 months, respectively.

CONCLUSION Our study showed clear differences between pIBD and aIBD, especially in UC. pUC presents with more extensive diseases and may have a more severe disease course, as suggested by an earlier time to administering medications and performing colectomy.