Hypersensitivity Reaction to Ustekinumab in Pediatric and Young Adult Inflammatory Bowel Disease Patients: A Case Series

Ustekinumab (UST) is a human IgG1K monoclonal antibody that binds to the p40 receptor subunit bound by cytokines IL-12 and IL-23. It is indicated in both Crohn’s disease and ulcerative colitis as a second-line agent. The safety and efficacy of UST in children and young adults has not been thoroughly studied. We report a case series of six pediatric patients and young adults who developed hypersensitivity reactions during intravenous infusion with UST. These reactions ranged from mild allergic reactions to anaphylaxis, with no detectable antibodies if tested. We hypothesize the reaction could be secondary to ethylenediaminetetraacetic acid, which is present solely in the intravenous preparation. Patients who experience hypersensitivity reactions during their UST infusion may safely receive subcutaneous preparations of UST, as demonstrated by some patients who received it based on physician discretion. Further investigation is required to establish the etiology of infusion reactions.