Outcome of Very Early Onset Pediatric Inflammatory Bowel Diseases Compared to Later-Onset Pediatric IBD: The 15-Year Single-Center Experience of a Referral Pediatric IBD Unit

Background: In last years, research interest increased for very early onset (VEO) inflammatory bowel disease (IBD), defined by age at diagnosis < 6 years. Previous works reported more severe disease course of VEO-IBD, compared with later-onset pediatric IBD, mainly attributed to a greater role of genetics in this age group. Otherwise, some studies questioned these results and reported comparable outcomes. Our study aimed to verify the effective role of age as a predictive factor of severity in the disease course. Methods: In this referral IBD single-center retrospective observational study, VEO-IBD was compared with IBD diagnosed between 6 and 17 years of age (ped-IBD). Patients with monogenic-IBD or IBD-like disease were excluded. We chose a minimum follow up period of 18 months since the diagnosis or any period in patients with Ulcerative Colitis (UC) who underwent surgery. The two cohorts were homogeneous for extension of disease and clinical severity at diagnosis and were compared for different clinical outcomes. Primary outcomes were the cumulative incidence of biological therapy use and the cumulative incidence of major surgery, as severity disease' indices. Secondary outcomes were the cumulative incidence of clinical remission, steroid-dependence and the relapse free survival at the last follow up. Results: 29 VEO-IBD cases were compared with 52 ped-IBDs. Median follow up time was 4,9 years. UC were most represented in both groups (83% of VEO-IBD, 81% of ped-IBD). At the end of follow up, the surgical rate was significantly higher for VEO-UC group compared with ped-UC (p 0.018). No difference in biologic therapy use was detected (45,6% VEO-IBD vs 43,5% ped-IBD; p 0.72). Cumulative incidences of relapse free survival, steroid-dependence, use of immunosuppressive therapy and clinical remission at the end of follow up were comparable. Discussion: Our data question the evidence of a worse outcome of VEO-UC, in comparison with ped-UC. Notably, we demonstrate a higher need for surgery in VEO-UC.