Tuesday, May 13, 2008 Metabolic newborn screening program
(Conclusion)
Glucose-6 Phosphate Dehydrogenase Deficiency
Glucose-6 phosphate dehydrogenase deficiency (G6PD) is a hereditary enzyme defect that can result in anemia. G6PD deficiency is the most common known human enzyme disease, affecting 10% of the world's population.
Over 400 million people worldwide have G6PD deficiency. G6PD deficiency can be found in virtually any population. However, it affects men of African descent most commonly. Females of African ancestry are less likely to demonstrate manifestations of the disease. Other affected populations include those of Asian or Mediterranean ethnic origins.
The abnormal gene responsible for this inherited enzyme deficiency is located on the X-chromosome.
Therefore, the illnesses associated with G6PD deficiency occur more frequently in males than females, since males only have one X-chromosome. There are different degrees of G6PD deficiency, which vary according to the magnitude of the missing enzyme.
People with this deficiency are not normally anemic. Instead, they may have occasional episodes when their red blood cells break down and stop functioning because they either suffer from certain infections or diabetic ketoacidosis or they have been exposed to certain oxidizing drugs and agents including: a) anti-malaria medications b) sulfonamides (antibiotic), mothballs or fava beans
G6PD deficiency is sometimes referred to as favism since some G6PD deficient individuals -- typically those of Mediterranean origin -- react severely to fava beans. Favism is potentially one of the gravest clinical consequences of G6PD deficiency.
It occurs more commonly in children than adults. A hemolytic crisis can develop quite suddenly, typically within the first 24 hours after exposure to fava beans. In some cases, the onset of hemolysis is noticed one or two days after ingesting the beans.
It is quite rare for someone with G6PD deficiency to experience a hemolytic crisis, but the crisis is an extremely serious condition that can result in death.
Hemolytic anemia occurs when the bone marrow is unable to compensate for premature destruction of red blood cells by increasing their production.
When the marrow is able to compensate, anemia does not occur. But when the destruction of red blood cells is so rapid the body can't keep up with production, anemia results. The most common symptoms of anemia include: tiredness, weakness, lightheadedness upon arising from a laying or sitting position and paleness which could show as pale skin, paleness around the gums, nails, or the linings of the lower eyelids.
If the rapid destruction of red blood cells is massive then overloading of the kidneys with free hemoglobin occurs. Hemoglobin is the protein found in red blood cells that carries oxygen to all parts of the body. It is the kidneys' job to cleanse the blood of impurities.
During this massive destruction of red blood cells called Hemolytic Crisis, the kidneys are unable to keep up with the workload.
Hemolytic crises in G6PD deficiency can be fatal. Signs of a crisis are: shortness of breath, rapid heart rate, yellow skin color (jaundice) most especially in the newborn period, dark urine, and an enlarged spleen.
Screening as well confirmation can be done in the newborn period especially in areas where G6PD is prevalent. The diagnosis is made by blood testing which can demonstrate the inadequate levels of the G6PD enzyme activity by blood testing.
There is no cure for the G6PD deficiency. However, large studies have shown that G6PD-deficient individuals do not acquire any illnesses more frequently than the rest of the population. By avoiding certain foods and drugs and by taking care of oneself to minimize infection, a person with G6PD deficiency can lead a normal life and have a normal life expectancy.
Treatment of G6PD deficiency involves discontinuing the offending drug or compound and treating any accompanying infection. A typical episode of hemolytic anemia, no treatment is needed other than identifying and stopping the cause for the episode. Recovery takes place in about eight days. However, in severe cases, blood transfusions are necessary. Alternative treatment with vitamin E and folic acid (both anti-oxidants) may be helpful in decreasing hemolysis.
Listed below are the drugs or chemical agents that may precipitate G6PD:
