- M" for methemoglobin), or Deficiency of the enzyme methemoglobin reductase which is required for the reduction of methemoglobin to normal oxyhemoglobin. In both kinds of congenital methemoglobinemia, the cyanosis starts in early infancy with no history of lung or heart disease to account for it. However, the patterns of inheritance deficiency are distinctively different — autosomal dominant with Hb M disease versus autosomal recessive with the enzyme deficiency. The cyanosis from Hb M disease is resistant to treatment with reducing agents such as ascorbic acid or methylene blue, whereas with deficiency of the enzyme, the cyanosis is typically improved by ascorbic acid or methylene blue therapy.
* * *The presence of methemoglobin in the circulating blood; when severe, there is inadequate oxygenation of the tissues. Methemoglobin causes the blood to have a brownish color, which may be mistaken for cyanosis. [methemoglobin + G. haima, blood]- acquired m. m. caused by various chemical agents, such as nitrites or topical anesthetics. SYN: enterogenous m., secondary m..- congenital m. 1. m. 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. m. 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; SYN: hereditary m., hereditary methemoglobinemic cyanosis, primary m..- secondary m. SYN: acquired m..
* * *met·he·mo·glo·bi·ne·mia or chiefly Brit met·hae·mo·glo·bi·nae·mia .met-.hē-mə-.glō-bə-'nē-mē-ə n the presence of methemoglobin in the blood due to conversion of part of the hemoglobin to this inactive form
* * *met·he·mo·glo·bin·emia (met″he-mo-glo″bĭ-neґme-ə) [methemoglobin + -emia] the presence of excessive methemoglobin in the blood, resulting in cyanosis and headache, dizziness, fatigue, ataxia, dyspnea, tachycardia, nausea, vomiting, and drowsiness, which can progress to stupor, coma, and occasionally death.
Medical dictionary. 2011.
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methemoglobinemia — noun Etymology: New Latin Date: 1888 the presence of methemoglobin in the blood … New Collegiate Dictionary
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methemoglobinemia — met·hemoglobinemia … English syllables
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congenital methemoglobinemia — hereditary methemoglobinemia any of several rare types caused by inherited conditions. Deficiency of cytochrome b5 reductase is an autosomal recessive condition that may be either confined to the erythrocytes and relatively symptom free or… … Medical dictionary