Anaphylaxis during the first course of high-dose methotrexate: a case report and literature review

What is known and Objective: Methotrexate (MTX) is widely used in the management of paediatric cancer with a generally favourable benefit/risk profile. We report an unusual adverse drug reaction with the first course of high-dose MTX in a paediatric patient and review the literature for similar cases. Case summary:  An 11-year-old boy with small-cell osteoblastic osteosarcoma in the lower limb experienced a case of life-threatening anaphylaxis during the first course of high-dose MTX. The adverse event occurred during the first course, likely due to an immune-mediated mechanism. We postulate that prior antineoplastic treatment might have contributed to the immune response to MTX. What is new and Conclusion:  Given that this reaction has rarely been reported, we discuss the present case with a review of other similar cases. Further studies are needed to substantiate this 'signal alarm' for serious MTX-related hypersensitivity reactions.