Environmentally-induced methemoglobinemia in an infant

Acquired methemoglobinemia results from the exposure to various chemicals and drugs able to oxidize hemoglobin at a rate exceeding the normal enzymatic capacity for hemoglobin reduction. Levels of methemoglobin exceeding 60-70% may be associated with coma and death. We describe a case of complete, uneventful recovery involving a 10 week-old infant who presented to the Emergency Department with profound sudden onset of cyanosis, irritability, metabolic acidosis, and a lethal methemoglobin level of 71.4%. Intravenous administration of 12 mg methylene blue resulted in immediate resolution of the cyanosis and reduction of measured methemoglobin to 1.3%. The carboxyhemoglobin was negative. Sodium bicarbonate successfully corrected the acidosis. RBC reductase measurement was within normal limits, ruling out congenital methemoglobinemia. Family history revealed a wood-burning stove which emitted pine tar fumes as the potential environmental methemoglobin-producing source. The infant's cradle was situated five feet from the stove. The infant was discharged on day three of hospitalization with a methemoglobin level of 0.2%.