Severe allergic reaction to ustekinumab reinitiation in a pediatric patient with Crohn's disease: A case report

Abstract Ustekinumab (UST) is a monoclonal antibody used in the management of moderate to severe inflammatory bowel disease. While generally well‐tolerated, serious adverse reactions, including hypersensitivity and anaphylaxis, have been documented, specifical following the initial intravenous (IV) dose. There is limited literature on hypersensitivity reactions in pediatric patients, particularly after re‐induction with IV therapy. This case highlights a novel, previously unreported scenario of a severe allergic reaction in a 10‐year‐old female with Crohn's disease (CD) during her second, re‐induction IV dose of UST, despite prior tolerance and no detectable UST antibodies. This case emphasizes the need for continued monitoring during IV UST administration, even in patients with prior tolerability.