RESUMEN
Methotrexate is a versatile antineoplastic and immunosuppressive agent. We report a case of a young adult on the Cancer and Leukaemia Group B 10403 treatment protocol for B-cell acute lymphoblastic leukaemia. She has previously completed the induction and consolidation phases with good tolerance then started on Capizzi methotrexate during the interim maintenance phase. Few days after receiving one intermediate dose of methotrexate, she developed severe multiorgan toxicities including pancytopaenia and several dermatologic toxicities. The patient underwent extensive diagnostic workup, with all results negative, pointing eventually towards severe methotrexate toxicity. This case highlights the broad spectrum of toxicities that can occur even with low doses of methotrexate. Capizzi methotrexate therapy implies no leucovorin therapy, hence putting patients at risk for multiorgan toxicity. Our experience reinforces the importance of close monitoring for patients receiving methotrexate, regardless of dose, and the prompt administration of high-dose leucovorin once toxicity suspected.