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Alternative Names Return to topHemoglobin M disease; Erythrocyte reductase deficiency; Generalized reductase deficiency
Definition Return to top
Methemoglobinemia is a blood disorder in which the body cannot recycle hemoglobin after it is damaged. 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.
Causes Return to top
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 an autosomal recessive condition. This means it is passed on by both parents who usually do not have the condition themselves but carry the gene that causes the condition. It occurs when there is a problem with an enzyme called cytochrome b5 reductase. There are two subtypes of autosomal recessive methemoglobinemia:
The second form of inherited methemoglobinemia, called hemoglobin M disease, is caused by defects in the hemoglobin molecule itself. It is an autosomal dominant condition. That means only one parent needs to pass you the abnormal gene in order for you 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).
Symptoms Return to top
Symptoms of type 1 methemoglobinemia (erythrocyte reductase deficiency) include:
Symptoms of type 2 methemoglobinemia (generalized reductase deficiency) include:
Symptoms of hemoglobin M disease include:
Symptoms of acquired methemoglobinemia include:
Exams and Tests Return to top
Methemoglobinemia can be diagnosed with a blood test.
A baby with this condition will have bluish skin color (cyanosis) at birth or shortly thereafter. Arterial blood gases and pulse oximetry results will be normal, making the condition challenging to diagnose.
Treatment Return to top
A medicine called methylene blue is used to treat persons with severe methemoglobinemia. Note: Methylene blue may be dangerous in patients who have or may be at risk for a blood disease called G6PD deficiency, and should not be used. If you or your child have G6PD deficiency, always tell the health care provider before treatment is given.
Ascorbic acid may also be used to reduce the level of methemoglobin.
Alternative treatments include hyperbaric oxygen therapy and exchange transfusions.
In most cases of mild acquired methemoglobinemia, no treatment is required, other than avoiding the medicine or chemical that caused the problem. Treatment, such as a blood transfusion, may be needed in severe cases.
Outlook (Prognosis) Return to top
People with Type 1 methemoglobinemia and hemoglobin M disease usually do well. Type 2 methemoglobinemia is much more serious, and usually causes death within the first few years of life.
People with acquired methemoglobinemia usually do very well once the drug, food, or chemical that caused the problem is avoided.
Possible Complications Return to top
When to Contact a Medical Professional Return to top
Call your health care provider if there is a family history of methemoglobinemia and you develop symptoms of this disorder.
Call your health care provider or emergency services immediately if there is severe shortness of breath.
Prevention Return to top
Genetic counseling is recommended for couples with a family history of methemoglobinemia who are considering having children.
References Return to top
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 SJ, Furie B, Cohen HJ, eds. Hematology: Basic Principles and Practice. 4th ed. Philadelphia, PA: Churchill Livingston Elsevier; 2005: chap 39.Update Date: 7/17/2008 Updated by: Linda Vorvick, MD, Seattle Site Coordinator, Maternal & Child Health Lecturer, Pathophysiology, MEDEX Northwest Division of Physician Assistant Studies, University of Washington School of Medicine. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.