LAUSR

To the Editor, Clofarabine is a secondgeneration purine nucleoside analogue approved for the treatment of refractory/relapsed pediatric acute leukemias.1,2 Reports of hypersensitivity reactions (HRs) to clofarabine are rare,3,4 and no such cases have been reported in children. HRs can manifest with a broad spectrum of symptoms, from mild cutaneous findings like maculopapular exanthema, urticaria to severe anaphylaxis.5 However, discontinuing a drug because of HRs increases the risk of a poor clinical outcome of the principal disease. Therefore, premedication and/or desensitization should be considered as alternative options when the drug is essential for treatment. Herein, we present a patient who had an HR during clofarabine infusion and was able to continue treatment with desensitization. A 17yearold boy was diagnosed with acute myeloid leukemia (AML) in the pediatric hematology department and received a myeloablative conditioning regimen consisting of clofarabine, cytarabine, and total body irradiation starting 10 days before planned allogeneic stem cell transplantation.1 The first intravenous infusion of clofarabine was planned at a dose of 52 mg/m2 administered over 2 h, following hydrocortisone premedication. During the first infusion, the patient described burning in his chest. When the infusion rate was decreased, his complaint regressed and the first infusion treatment was completed successfully. On the second day of treatment, the patient developed an erythematous rash on both arms despite starting the second infusion at a lower rate (over 4 h). When the patient's vital signs were evaluated, his arterial blood pressure was measured as 90/30 mm Hg and the infusion was stopped. The patient's symptoms regressed after stopping treatment. He had received steroid treatment as a part of his regimen, and this may have masked some of his symptoms. As he had to take the drug urgently for his treatment, there was no time for diagnostic allergy tests; therefore, it was not possible to distinguish whether the reaction was an immunoglobulin E (IgE)mediated or nonimmunological reaction. Desensitization was planned for the patient because there was no suitable alternative chemotherapeutic agent to treat his AML and clofarabine was an essential part of treatment. After obtaining informed consent, a desensitization protocol with 3 dilutions and 12 steps was planned. Based on the normal therapeutic dose required by the patient, solutions of 0.005, 0.05, and 0.5 mg/mL were prepared (Table 1). Each solution was used for 4 steps, with the entire 12step protocol completed in 4 h and 26 min.