Background: Few studies have compared phenotype and disease course in children and adults with inflammatory bowel disease (IBD).

Objective:   To compare phenotype, treatment and disease course in children (<15 years) and adults (≥18 years) with IBD.

Methods: Two population-based cohorts comprising paediatric (2001-2006) and adult (2003-2004) patients from Copenhagen County and City were studied.

Results: Twenty children and 106 adults with ulcerative colitis (UC), and 29 children and 67 adults with Crohn's disease (CD) were included. Median follow-up time was 4.8 years (children) and 5.2 years (adults). Children with UC had more extensive disease compared to adult patients [14 (70%) vs. 20 (19%), P<0.001]. The risks of starting systemic steroid treatment and AZA/MP were higher for paediatric UC patients compared to adult UC patients; hazard ratio (HR): 3.1 (95% CI: 1.8-5.3) and HR: 2.5 (1.3-5-9), respectively. Steroid dependency was more frequent in paediatric than in adult UC patients [9 (45%) vs. 9 (8%), P<0.001]. Mild disease course was less frequent in children with UC compared to adult patients [7 (35%) vs. 76 (72%), P=0.002]. Paediatric and adult CD patients did not differ regarding treatment or disease course. Cumulative 5-year surgery rates for paediatric and adult patients were 5% and 9% for UC (N.S.) and 18% and 21% for CD (N.S.), respectively.

Conclusions: Paediatric UC patients had more extensive disease, were more often treated with systemic steroids and AZA, had a higher frequency of steroid dependency and a more severe disease course compared to adult UC patients. No differences were found when comparing paediatric and adult CD patients.