Case of Acetaminophen overdose leading to mixed sulfhemoglobinemia and methemoglobinemia: A report

The authors present a case of mixed sulfhemoglobinemia and methemoglobinemia in the setting of a large, untreated ingestion of acetaminophen exacerbated by the administration of methylene blue due to occult G6PD deficiency. There is no clarity on the ultimate cause of the patient's dyshemoglobinemias; they hypothesized that acetaminophen-induced oxidative stress triggered the formation of both sulfhemoglobin and methemoglobin. There needs to be more clarity on the role of G6PD deficiency as a risk factor for sulfhemoglobinemia formation. They acknowledged that a lack of comprehensive laboratory screening limits the report and that we cannot exclude an occult, alternative causative agent entirely.

The authors conclude that acetaminophen overdoses presenting with methemoglobinemia should prompt concern for underlying G6PD deficiency.

"Early consideration of coincidental sulfhemoglobinemia should be done if the pulse oximetry is lower and the patient appears more symptomatic than the measured methemoglobin concentration alone would suggest," they wrote. "However, confirmation of sulfhemoglobinemia will be delayed in most conditions."

"These factors prompted methylene blue use in this case, despite the low measured percentage of methemoglobin, which likely triggered hemolytic anemia," the team explained. "The use of methylene blue in a similar circumstance, regardless of the underlying cause, should be weighed carefully against iatrogenic harm risk."

Reference:

Seltzer, Justin A., et al. "Sulfhemoglobinemia and Methemoglobinemia Following Acetaminophen Overdose." Toxicology Reports, vol. 9, 2022, pp. 1725-1727.