The New England Journal of MedicineCentral Cyanosis in Acquired Methemoglobinemia

Linking Dapsone Use to Acquired Methemoglobinemia in Leprosy Treatment

A recent clinical case highlights the occurrence of acquired methemoglobinemia in a patient undergoing multidrug therapy for leprosy with dapsone. Despite negative testing for glucose-6-phosphate dehydrogenase deficiency, the patient developed significant symptoms and cyanosis, raising crucial considerations for monitoring and management in similar therapeutic contexts. This case serves as an important reminder for clinicians of the potential hematological complications associated with dapsone, even in patients without evident predisposing factors.

Key Points:

• A 35-year-old man developed anxiety, insomnia, and tremor after starting multidrug therapy for leprosy, including dapsone.
• Symptoms included bluish discoloration of the lips and tongue, recognized as central cyanosis, indicative of potential oxygen transport issues.
• Although arterial blood gas analysis showed normal oxygen partial pressure (Pao2) of 96 mm Hg, oxygen saturation was low at 84%, revealing a saturation gap.
• The diagnosis of acquired methemoglobinemia was considered based on the discrepancy between Pao2 and oxygen saturation, a known possible side effect of dapsone.
• Methemoglobin levels were found to be elevated at 14%, significantly above the normal range (0-3%).
• Upon discontinuation of dapsone and initiation of supportive care, the patient’s symptoms and cyanosis resolved within two days.

The first reported case of fatal acquired methemoglobinemia (“Blue Baby Syndrome”) in an infant due to ingestion of nitrate contaminated well water in the United States occurred in 1945, and in the following 25 years, about 2,000 similar cases of acquired methemoglobinemia in young infants were reported worldwide; about 10% of such cases resulted in death. (CDC)

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