Incidence, Disease Course, and Medical Treatment of a Danish Population-Based Cohort of Very Early-Onset Inflammatory Bowel Disease

Background and Aims. In very early-onset IBD patients (VEO-IBD), studies have shown an incidence ranging from 0.4 to 2.1/100,000, extensive disease location, and a corresponding difficult and debatable treatment. We therefore aimed to investigate the incidence and medical and surgical treatment of VEO-IBD in a well-defined Danish population-based cohort. Methods. All VEO-IBD patients, defined as an IBD diagnosis before 6 years of age, were included from the Capital Region and the Zealand Region in 2015-2020. Demographic and clinical data including medical and surgical treatment were systematically extracted from the patient files. Results. Forty VEO-IBD patients were identified, 11 diagnosed with CD, 23 UC, and 6 IBD-U. The incidence rate of VEO-IBD was 2.0/100,000 (95% CI 0.8-5.9). All VEO-IBD patients except one had extensive colonic involvement or pancolitis. A total of 34 (85.0%) and 23 (57.5%) of the VEO-IBD patients received immunomodulators and/or biologicals, respectively. The cumulative risks of receiving immunomodulators and/or biologicals after 1/3/5 years was 55.3%/86.8%/90.1% and 36.8%/45.9%/57.0%, respectively. During follow-up, six VEO-IBD patients (15.0%) were treated with vedolizumab—although off-label for this age group—as second-line biological therapy. Four patients (17.4%) with UC had a colectomy. Two colectomised patients were treated with vedolizumab. Conclusion. Our population-based study showed an incidence of VEO-IBD comparable with the incidence in other countries. The population were treated intensively with immunomodulators and biologicals—including off-label vedolizumab—and compared to other studies had the same risk of undergoing IBD-related surgeries.