Rasburicase-Induced Methemoglobinemia in a Patient with Glucose-6- Phosphate Dehydrogenase Deficiency.

BACKGROUND: Rasburicase is commonly used in patients with hematologic malignancies for tumor lysis syndrome prophylaxis and management. Methemoglobinemia is a serious rare adverse effect of rasburicase, more common in patients with G6PD deficiency. Prompt diagnosis and appropriate management of this condition can make the difference between successful recovery and significant morbidity. Here we discuss the link of rasburicase with methemoglobinemia and the pathophysiology behind increased incidence of this side effect in G6PD deficient patients.

METHODS: We report the case of a 73-year-old African American man who developed methemoglobinemia on rasburicase treatment, who was later confirmed to be G6PD deficient. We reviewed the literature using Pubmed and Google Scholar using the following key words: "methemoglobinemia", "rasburicase", "urate oxidase", tumor lysis syndrome", G6PD deficiency", "hemolytic anemia" and "hyperuricemia".

RESULTS: Rasburicase-induced methemoglobinemia is more common in patients with G6PD deficiency, and rasburicase is therefore contraindicated in these patients. Clinical presentation includes cyanosis, pallor, methemoglobin levels of 8-12%, and oxygen saturation gap which is evident from ABG analysis, though pulse oximetry is normal. Treatment consists of oxygen supplementation, ascorbic acid and blood transfusion. Importantly, methylene blue is avoided as therapy in G6PD deficiency as it can worsen the methemoglobinemia.

CONCLUSION: Rasburicase-induced methemoglobinemia is a serious concern, especially in African- American patients. It should be considered when clinical signs and symptoms are present. Knowledge of this side effect is important in early diagnosis and successful management of the condition.