Methemoglobinemia induced by rasburicase in a pediatric patient: a case report and literature review.

Rasburicase is a recombinant urate oxidase enzyme indicated for tumor lysis syndrome (TLS), a potential life-threatening oncologic emergency that occurs most commonly during chemotherapy for hematological malignancies. As a result of the defects in the physiological antioxidant pathway, erythrocytes of patients with glucose-6-phosphate dehydrogenase (G6PD) deficiency are not protected against the oxidating stress exerted by hydrogen peroxide generated with the administration of rasburicase. Therefore, rasburicase is contraindicated in patients with known G6PD deficiency and the manufacturer recommends screening all patients with high risk for G6PD deficiency before initiating rasburicase therapy. However, it is logistically difficult in clinical settings because of the high risk of morbidity and mortality associated with TLS if treatment is delayed and the long turnaround time of the G6PD deficiency screening. Therefore, administering rasburicase to patients developing TLS before confirming a patient's G6PD status is practically inevitable. Methemoglobinemia, and/or hemolysis, may result from the oxidative stress. Descriptions of the clinical course should it happen are limited in the literature. There are eight reported cases of rasburicase-related methemoglobinemia, with or without hemolytic anemia, in the literature of which five are pediatric patients. Six reports (including three pediatric patients) had detailed descriptions of the event and management. The recent reports of methemoglobinemia observed in patients with probable G6PD activity further complicated the picture. We are reporting a 16-year-old patient diagnosed with Burkitt's lymphoma who developed methemoglobinemia after receiving one dose of rasburicase. He was managed by transfusion and oxygen support. The patient recovered well and the observed methemoglobinemia was reversible.