Early Onset Inflammatory Bowel Disease Due to Immunodeficiency as a Result of ICOS Gene Homozygous Mutation

Introduction:Inflammatory bowel disease (IBD) is classified as very early-onset IBD (VEO-IBD) if it occurs before age six. VEO-IBD may progress with more severe and resistant inflammation findings in the gastrointestinal and non-gastrointestinal systems.Case report:We describe the clinical presentation of a 4-year-old female presenting with recurring episodes of bloody diarrhea, vomiting, abdominal pain, fever, arthritis, erysipelas, and bilateral ankle pain. Monogenic primary immunodeficiency (PID) was suspected due to her age, different clinical findings and the presence of atypical gastroscopic findings and deep transmural ulcerations resembling Crohn's disease. The gene analysis showed a homozygous mutation in the inducible T cell co-stimulator (ICOS) deficiency genes.Discussion/Conclusion:This case presentation shares our clinical experience and demonstrates the link between IBD progression and ICOS deficiency.