Clinical phenotypes of very early onset inflammatory bowel disease in Australian children: A single-centre retrospective study

Very early onset inflammatory bowel disease (VEO-IBD), diagnosed at <6 years old, includes a subset of infantile onset IBD (IO-IBD, ≤2 years). We describe presenting clinical features, phenotypes, and early management of children with VEO-IBD at a single tertiary centre.

Retrospective cohort study of children with VEO-IBD diagnosed at Queensland Children's Hospital from January 2010 to March 2025.

In 52 children, (24 IO-IBD; 28 VEO-IBD), median Paediatric Ulcerative Colitis Activity Index on presentation was 35 (interquartile range [IQR] 15), similar in both groups (35 IO-IBD; 39.5 VEO-IBD). Ulcerative colitis (UC) was the most frequent diagnosis (50%; 38% Crohn's disease; 12% IBD-Unclassified [IBD-U]). Among children with UC/IBD-U, pancolitis was common in both groups (57.1% IO-IBD; 66.7% VEO-IBD). Paris-classified anatomic phenotype did not differ between IO-IBD and VEO-IBD. Atypical colitis, upper gastrointestinal involvement, and granulomas occurred in 23%, 38% and 35% of cases, respectively. Prior allergic/atopic diagnoses were documented in 44%. Primary sclerosing cholangitis (PSC) was identified in 8% within 12 months of IBD diagnosis. Two monogenic disorders were identified, among 38 genotyped children, with severe perianal disease and successful bone marrow transplantation. Corticosteroids were used in 67% (35/52); 86% (30/35) responded without biologic rescue; five required anti-tumour necrosis factor therapy. One child required early colectomy.

IO-IBD and VEO-IBD demonstrated substantial overlap in presenting clinical and intestinal phenotypes. Monogenic disease was confined to IO-IBD, while early PSC was a notable secondary finding. These data support phenotype-guided genetic evaluation and further study of early hepatobiliary disease in VEO-IBD.