Leukocyte Larceny in AML: A Case of Falsely Low Oxygen Levels - Case Report

Hyperleukocytosis in acute myeloid leukemia (AML) can cause life-threatening complications and rarely “leukocyte larceny,” in which markedly elevated blasts consume oxygen in arterial blood gas (ABG) samples, producing spuriously low PaO₂ values. We report an 82-year-old man with newly diagnosed AML and WBC 310.8 × 109/L who developed hypoxic respiratory failure requiring intubation. Despite low post-intubation PaO2, pulse oximetry remained consistent with adequate oxygenation, suggesting partially spurious hypoxemia in the setting of true respiratory compromise. Cytoreduction was initiated; however, his course was complicated by tumor lysis syndrome, renal failure, shock, and death. This case highlights the diagnostic pitfall of leukocyte larceny that may complicate clinical decision-making and emphasizes the importance of correlating ABG results with pulse oximetry and considering rapid sample processing or cooling to reduce in vitro oxygen consumption.