Glucose-6-phosphate dehydrogenase deficiency

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Alternative names
G-6-PD deficiency; Hemolytic anemia due to G6PD deficiency; Anemia - hemolytic due to G6PD deficiency

Definition
G-6-PD deficiency is a hereditary, sex-linked enzyme defect that results in the breakdown of red blood cells when the person is exposed to the stress of infection or certain drugs.

Causes, incidence, and risk factors

G-6-PD deficiency is an inheritable, X-linked recessive disorder whose primary effect is the reduction of the enzyme G-6-PD in red blood cells, causing destruction of the cells, called hemolysis. Ultimately, this hemolysis leads to anemia—either acute hemolytic or a chronic spherocytic type.

In the United States, many more black than white people have the disorder. Approximately 10-14% of the black male population is affected. The disorder may occasionally affect a black women to a mild degree (depending on their genetic inheritance).

People with the disorder are not normally anemic and display no evidence of the disease until the red blood cells are exposed to an oxidant or stress.

Drugs that can bring on this reaction include:

• antimalarial agents
  
• sulfonamides (antibiotic)
  
• aspirin
  
• nonsteroidal anti-inflammatory drugs (NSAIDs)
  
• nitrofurantoin
  
• quinidine
  
• quinine
  
• others

It can also be caused by exposure to certain chemicals, such as those in mothballs. The chronic spherocytic anemia is unaffected by exposure to these drugs.

The risk of acute hemolytic crisis can be decreased by reviewing the family history for any evidence of hemolytic anemias or spherocytosis or testing before giving any medications belonging to the above class of chemicals.

The episodes are usually brief, because newly produced (young) red blood cells have normal G6PD activity.

Risk factors are being black, being male, or having a family history of G6PD deficiency. Another type of this disorder can occur in whites of Mediterranean descent. This form is also associated with acute episodes of hemolysis. Episodes are longer and more severe than in the other types of the disorder.

Symptoms

• Fatigue
  
• Paleness
  
• Shortness of breath
  
• Rapid heart rate
  
• Yellow skin color (jaundice)
  
• Dark urine
  
• Enlarged spleen

Note: Severe hemolysis may cause hemoglobinuria (hemoglobin in the urine).

Signs and tests

• Anemia
  
• Hemolysis
  
• Reduced G-6-PD activity
  
• Reticulocytosis following a hemolytic crisis

Tests include:

• Elevated bilirubin levels
  
• Elevated serum LDH
  
• Low serum haptoglobin
  
• Hemoglobin in the urine
  
• Elevated absolute reticulocyte count
  
• Low red blood cell count and hemoglobin
  
• Heinz bodies present on examination of the peripheral blood smear using special stains
  
• Methylene blue test
  
• Methemoglobin reduction test

Treatment
If the cause is an infection, it should be treated. If the cause is a drug, the offending agent should be stopped. People with the Mediterranean form, or those in hemolytic crisis may occasionally require transfusions.

Expectations (prognosis)
Spontaneous recovery from hemolytic crises is the usual outcome.

Complications
Rarely, kidney failure or death may occur following a severe hemolytic event.

Calling your health care provider
Call for an appointment with your health care provider if symptoms of hemolytic anemia due to G-6-PD deficiency develop.

Call your health care provider if you have G-6-PD deficiency and symptoms of hemolytic anemia do not disappear after treatment of the cause.

Prevention
People with G-6-PD must strictly avoid factors that can precipitate an episode, especially drugs known to cause oxidative reactions.

Genetic counseling or genetic information may be of interest to heterozygous women and affected men.

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