Methemoglobinemia overview

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]

Overview

Methemoglobinemia (congenital or acquired) is a blood disorder in which, due to increased production, the red blood cells (RBCs) contain abnormal hemoglobin, called methemoglobin (MetHb) at levels higher than 1%. The formation of methemoglobin results from the substitution of iron (Fe) in ferric (Fe²⁺) form, as found in normal hemoglobin, with iron in a reduced (Fe³⁺) form. Hemoglobin is the polypeptide protein in red blood cells (RBCs) that binds, carries and distributes oxygen from the lungs to the tissues, consisting of 2 alfa and 2 beta chains, connected with an iron atom in ferric form. In MetHb the affinity to oxygen is greatly increased, which leads to decreased release of oxygen to the tissues.