Not the Typical Pneumonia: An Unusual Case of Rasburicase-induced Methomoglobinemia

We present a rare case of rasburicase-induced methemoglobinemia and hemolytic anemia in the setting of presumed glucose-6-phosphate dehydrogenase (G6PD) deficiency. A 78-year-old male with a known history of chronic lymphocytic leukemia presented to the clinic with fever of unknown origin. Laboratory results were significant for hyperuricemia. He was empirically started on levofloxacin and rasburicase. He then presented to the emergency department with shortness of breath and syncope. Physical examination was remarkable for a fever of 102.8 °F, conjunctival pallor, and scleral icterus. An infiltrate was observed on his computed tomography (CT) angiogram of the chest. Arterial blood gas on 50% fraction of inspired oxygen was significant for an arterial oxygen level of 222 millimeters mercury and oxyhemoglobin of 85.9%. Co-oximetry was then obtained and methemoglobin level was 13.4%. Laboratory results were noteworthy for a drop-in hemoglobin, indirect hyperbilirubinemia, low haptoglobin and elevated lactate dehydrogenase; depicting hemolytic anemia. The patient received two units of packed red blood cells, intravenous broad-spectrum antibiotics and he clinically improved.