Hemoglobin M disease; Erythrocyte reductase deficiency; Generalized reductase deficiency
Methemoglobinemia is a blood disorder in which an abnormal amount of hemoglobin builds up in the blood. Hemoglobin is the oxygen-carrying molecule found in red blood cells. In some cases of methemoglobinemia, the hemoglobin is unable to carry oxygen effectively to body tissues.
Methemoglobinemia may be passed down through families (inherited). Or, it may result from exposure to certain drugs, chemicals, or foods (acquired).
There are two forms of inherited methemoglobinemia. The first form is passed on by both parents. The parents usually do not have the condition themselves, but they carry the gene that causes the condition. It occurs when there is a problem with an enzyme called cytochrome b5 reductase.
There are two types of this form of methemoglobinemia:
The second form of inherited methemoglobinemia, called hemoglobin M disease, is caused by defects in the hemoglobin molecule itself. Only one parent needs to pass on the abnormal gene in order for the child to inherit the disease.
Acquired methemoglobinemia is more common than the inherited forms. It occurs after exposure to certain chemicals and drugs, including:
The condition may also occur in infants who are very ill or who are fed too many vegetables containing nitrates (such as beets).
DeBaun MR, Vichinsky E. Hemoglobinopathies. In: Kliegman RM, Behrman RE, Jenson HB, Stanton BF, eds. Nelson Textbook of Pediatrics. 18th ed. Philadelphia, PA: Saunders Elsevier; 2007:chap 462.
Gregg XT, Prchal JT. Red blood cell enzymopathies. In: Hoffman R, Benz EJ Jr., Shattil SS, eds. Hematology: Basic Principles and Practice. 5th ed. Philadelphia, PA: Elsevier Churchill Livingston; 2008:chap 45.
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