methaemoglobinaemiamedical dictionary

<haematology> A clinical condition in which more than 1% of the haemoglobin in the blood has been oxidized to the ferric (Fe3+) state.

The principle finding is cyanosis due to the oxidized haemoglobins inability to transport oxygen. Nitrites can cause this condition and it has been reported in commercial meat packers.

It may be drug-induced or be due to a defect in the enzyme NADH methaemoglobin reductase (an autosomal recessive trait) or to an abnormality in haemoglobin M (an autosomal dominant trait).

The presence of methaemoglobin in the blood, resulting in cyanosis. A small amount of methaemoglobin is present in the blood normally, but injury or toxic agents convert a larger proportion of haemoglobin into methaemoglobin, which does not function reversibly as an oxygen carrier.

Methaemoglobinaemia may be due to a defect in the enzyme NADH methaemoglobin reductase (an autosomal recessive trait) or to an abnormality in haemoglobin m (an autosomal dominant trait).

Treatment may include ascorbic acid or methylene blue.

American spelling: methemoglobinemia

Origin: Gr. Haima = blood

(12 Dec 1998)