Medical Definition of Methemoglobinemia

  • Medical Author:
    William C. Shiel Jr., MD, FACP, FACR

    Dr. Shiel received a Bachelor of Science degree with honors from the University of Notre Dame. There he was involved in research in radiation biology and received the Huisking Scholarship. After graduating from St. Louis University School of Medicine, he completed his Internal Medicine residency and Rheumatology fellowship at the University of California, Irvine. He is board-certified in Internal Medicine and Rheumatology.

Methemoglobinemia: The presence in the blood of methemoglobin, a form of hemoglobin that is useless for carrying oxygen and delivering it to tissues throughout the human body. A small amount of methemoglobin is normally present in blood but the conversion of a larger fraction of hemoglobin into methemoglobin, which does not function well as an oxygen carrier, results in clinical symptoms. Since hemoglobin is the key carrier of oxygen in the blood, its replacement by methemoglobin can cause a slate gray-blueness of the skin (cyanosis), and potentially cause more serious symptoms due to insufficient oxygen.

In more technical terms, methemoglobin is a transformation product of normal oxyhemoglobin. It is created by the oxidation of the ferrous iron present in the heme part of hemoglobin to ferric iron.

Methemoglobinemia may be acquired anytime in life by exposure to a number of different chemical agents such as nitrites or certain medications (acquired methemoglobulinemia) or it may be present at birth (congenital) due a genetic condition.

Reviewed on 12/11/2018


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REFERENCE: Methemoglobinemia in Emergency Medicine.

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