Acute hemolytic anemia and methemoglobinemia in a pediatric oncology patient with G6PD deficiency: a case report

Background: Glucose-6-phosphate dehydrogenase (G6PD) deficiency is a common enzymatic disorder that is often asymptomatic until exposure to oxidative stress, such as certain medications. Rasburicase, used for tumor lysis syndrome (TLS) prophylaxis, can trigger hemolysis in G6PD-deficient patients. Case presentation: We report a nine-year-old Asian boy with acute myeloid leukemia (AML) and hyperleukocytosis who developed severe hemolytic anemia and methemoglobinemia shortly after receiving rasburicase for TLS. Enzymatic testing suggested G6PD deficiency but was unreliable due to hyperleukocytosis. Rasburicase was discontinued, and supportive care with ascorbic acid led to rapid clinical improvement. Subsequent gene-panel analysis using whole exome sequencing (WES) confirmed a pathogenic class B G6PD variant (Viangchan). Conclusion: This case highlights the need for caution when administering rasburicase to patients with unknown G6PD status, particularly in individuals from regions or ethnic groups with a high prevalence of G6PD deficiency. Enzymatic testing may become unreliable due to hyperleukocytosis or recent transfusions. Therefore, close monitoring of hemolysis parameters with a low transfusion threshold in acute hemolytic anemia is essential. Genotyping using WES or whole genome sequencing (WGS) provides definitive G6PD variant classification. This enables careful dose adjustments and proactive monitoring for G6PD-related hemolysis caused by high-risk drugs in pediatric oncology.