congenital methemoglobinemia(redirected from primary methemoglobinemia)
1. methemoglobinemia due to formation of any one of a group of abnormal α chain [MIM*141800] or β chain [MIM*141900] hemoglobins collectively known as hemoglobin M. Slate-gray cyanosis occurs in early infancy, without pulmonary or cardiac disease, and is resistant to ascorbic acid or methylene blue therapy; autosomal dominant inheritance;
2. methemoglobinemia due to deficiency of cytochrome b5 reductase [MIM*250790] or methemoglobin reductase [MIM*250700], the enzyme responsible for reduction of intraerythrocyte methemoglobin; cyanosis is improved by ascorbic acid or methylene blue; autosomal recessive inheritance;
Elevated levels of methemoglobin in the blood, resulting from one of several hereditary deficiencies of methemoglobin reductase. Affected persons may appear mildly cyanotic but are rarely symptomatic.
See also: methemoglobinemia
con·gen·i·tal met·he·mo·glob·i·ne·mi·a(kŏn-jeni-tăl met-hēmō-glō-bi-nēmē-ă)
1. Methemoglobinemia due to formation of any one of a group of abnormal α chain or β chain hemoglobins collectively known as hemoglobin M.
2. Methemoglobinemia due to deficiency of cytochrome b5 reductase or methemoglobin reductase.
methemoglobin in the blood, usually due to the toxic action of drugs or other agents, or to hemolytic processes. The common cause in food animals is nitrite poisoning. Clinically there is dyspnea and sometimes coffee colored mucosae.
an inherited condition suspected in horses.