メトトレキサートの初回投与でアナフィラキシー様反応を呈した骨肉腫の1例

Anaphylactoid Reaction during Administration of the Initial Dose of Methotrexate in a Patient with Osteosarcoma. Case Report

　メトトレキサート（以下MTX）大量療法の初回にアナフィラキシー様反応を呈した，小児骨肉腫の1例を報告する．症例は10歳の男児で右大腿骨遠位部骨肉腫である．MTX12g/m²の初回投与で喘息様の咳と全身の蕁麻疹を生じたが，2回目以降はMTX投与前にステロイド剤と抗ヒスタミン剤を併用することで，術前・術後化学療法を無事完遂し得た．MTX初回投与でのアナフィラキシー様反応は極めて稀であるが注意が必要である．症状が重篤でない場合，ステロイド剤と抗ヒスタミン剤の併用で治療継続可能と思われた．

　Background：Methotrexate (MTX) is a chemotherapeutic agent osteosarcoma that is effective against, and rare anaphylactoid reactions to MTX have been reported, especially during the initial period of exposure. We report a case of osteosarcoma in which the patient developed anaphylactoid reactions during administration of the initial dose of high-dose MTX therapy.　Case Description：The patient was a 10-year-old boy with osteosarcoma of the right distal femur who developed generalized pruritus, urticaria, and wheezing within 30minutes of receiving the initial dose of high-dose MTX, 12g/m² body surface area. The infusion was terminated, and his symptoms abated after intravenous corticosteroid administration. After premedication with cortico-steroid and antihistamines, we succeeded in continuing administration of high-dose MTX as neoadjuvant and adjuvant chemotherapy. The total dose of MTX was 521g.　Conclusions：Careful patient monitoring is required to treat anaphylactoid reactions during both the initial exposure and subsequent exposures to MTX. Premedication with corticosteroids and antihistamines may allow continued administration of the MTX chemotherapy they require to osteosarcoma patients who experience anaphylactoid reactions to MTX.