Major causes of lower gastrointestinal bleeding in children by age group

IBD: inflammatory bowel disease; IgA: immunoglobulin A.

* Rarely, IBD presents before 6 years of age (denoted by striped bar). This presentation is sometimes termed very early-onset IBD (VEO-IBD), or infantile IBD if it presents before 2 years of age. This form of IBD is often associated with specific gene defects that cause an IBD-like disease by altering immune function or disturbing epithelial barrier function.