What is methemoglobinemia?

Updated: Dec 09, 2018
  • Author: Mary Denshaw-Burke, MD, FACP; Chief Editor: Emmanuel C Besa, MD  more...
  • Print
Answer

Methemoglobinemia (congenital or acquired) occurs when red blood cells (RBCs) contain methemoglobin at levels higher than 1%. Methemoglobin results from the presence of iron in the ferric form instead of the usual ferrous form. This results in a decreased availability of oxygen to the tissues. Symptoms are proportional to the methemoglobin level and include skin color changes and blood color changes at levels up to 15% (see the image below). As levels rise above 15%, neurologic and cardiac symptoms arise as a consequence of hypoxia. Levels higher than 70% are usually fatal.

Note chocolate brown color of methemoglobinemia. I Note chocolate brown color of methemoglobinemia. In tubes 1 and 2, methemoglobin fraction is 70%; in tube 3, 20%; and in tube 4, normal.

See Clues on the Skin: Acute Poisonings, a Critical Images slideshow, to help diagnose patients based on their dermatologic presentations.


Did this answer your question?
Additional feedback? (Optional)
Thank you for your feedback!