Written By: Hanan Khalaf. RPH
What is G6PD deficiency?
Glucose-6-phosphate dehydrogenase deficiency (G6PD deficiency), or what is commonly known as Favism as a broader term, is an enzyme deficiency and is one of the most common hereditary genetic disorder that was discovered in 1950s. This enzyme is produced in red blood cells (RBCs) and has 2 important functions:
It plays an important step in carbohydrate metabolism turning them to energy.It protects RBCs from oxidative stress by neutralizing oxidative substances that form as a result of infection or following administration of certain medication or even eating certain kinds of food.
All patients with favism have G6PD deficiency, but not all individuals with G6PD deficiency are susceptible to favism.
What causes G6PD deficiency?
G6PD deficiency is an inherited disorder in which the affected gene is located on the X-chromosome. Therefore, the illness associated with G6PD deficiency occurs more frequently in males than females, since males only have one X-chromosome (XY), while females have 2 X-chromosomes (XX), so if one chromosome is affected she will be carrier and will develop the disorder only if both chromosomes are affected, as what happens if she inherits mutated gene from both parents.
What are the risk factors for G6PD deficiency?
Ethnicity: G6PD deficiency is most common in African-Americans, and people of Mediterraneanheritage, including Italians, Greeks, Arabs, and Sephardic Jews. There is no good explanation for that, but researchers think this deficiency developed through generations as a protection against malaria (an infectious disease that is common in Africa and certain Mediterranean regions). It is known that the parasite causing malaria does not survive well in G6PD deficient persons.
Being a male.Family history of G6PD deficiency.
How does G6PD deficiency manifest?
People affected are not normally anemic and generally asymptomatic unless exposed to an oxidative stress. Such exposure can lead to hemolysis (rupture of red blood cells) and hemolytic anemia either acute or chronic spherocytic type. Hemolytic anemia can manifest, depending on severity, as follows:
FatiguePalenessRapid breathing or shortness of breath.Rapid heart rateYellow skin color (jaundice), including neonatal jaundice which could be prolonged and persistant, could be severe enough to cause death or permanent neurologic damage.Dark urineEnlarged spleen
Severity of the symptoms varies according to the ethnicity being most severe in people of Mediterranean origin and less severe in African-Americans
What are the consequences or complications of such hemolysis?
In most cases, hemolytic crises recover spontaneously with no complications following removal of the offending agent. Consequently, symptoms disappear quickly within few weeks with the generation of new RBCs that have not been exposed to the oxidative stress triggered by the prior illness, medication, or other agent, and the anemia will improve. Rarely, however, renal failure or even death might follow severe hemolytic crisis.
How can G6PD deficiency be diagnosed?
Diagnosing G6PD is easy and involves blood test that measures directly G6PD activity. In addition, complete blood count (CBC), blood smear (where blood is smeared onto a glass slide and the blood cells are examined under a microscope), and other blood tests might be done to rule out other causes of anemia. However, testing for heterozygous females requires specialized genetic labs.
What factors can trigger the occurrence of signs and symptoms?
Signs of G6PD deficiency usually start to appear when red blood cells are exposed to high level of oxidative stress. The degree of hemolysis varies according to the degree of enzyme deficiency and the magnitude of offending agent and is usually precipitated by:
Bacterial or viral infections.Exposure to some medications (list below). While some persons affected can tolerate those medications in small amounts, others cannot.Consumption of certain kind of food mainly fava beans, some persons might be affected by even touching them or inhaling their pollens.
Drug List: (by generic names), List is inclusive, not exclusive
Analgesics and Antipyretics:
Antimalarials:
Antibiotics:
Miscellaneous:
Aspirin
Acetanilide
Phenacetine
Antipyrine
Chloroquine.
Primaquine
Pamaquine
Quinine
Pyrimethamine
Mefloquine
Pyrimethamine/Sulfadoxime
Dapsone.
Nitrofurantoin.
Nalidixic acid.
Chloramphenicol.
Septrin.
Furazolidine
Methylene blue
Quinidine.
Niridazole.
Dimercaprol
Vitamin K
Probenicid.
Phenylhydrazine
Naphthalene.
Procainamide
Pyridium
Chronic hemolytic anemia is not affected by above mentioned drugs.
For a more complete list,
What diet precautions should be considered for persons affected with G6PD deficiency?Persons affected should strictly avoid Fava beans and all food made from them like
Foule modems, Falafel, and Bajela.
Some prefer also to avoid red wine, all legumes, blueberries [also yogurts containing these], soya products, tonic water).
Breast-feeding mother of G6PD deficiency baby should follow the diet as well.
Restrictions for the consumption of some Chinese herbs should be exercised and physician should be consulted before attempting to. For a complete list
Is there any treatment for G6PD deficiency?
There is no cure for G6PD deficiency and prevention is the key issue. Persons affected with this enzyme deficiency should strictly avoid any condition that might predispose to acute hemolysis. Should it happen, eliminating the offending agent and supportive measures are to be undertaken if indicated as bed rest, hydration, oxygen therapy. In more severe cases, blood transfusion might be required.
How can we decrease the risk of acute hemolytic crisis?
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 of the medications mentioned above.
Is there any specific age at which G6PD starts to manifest?
No, it can manifest at any age starting with neonates.
References:
http://www.kidshealth.org/parent/general/aches/g6pd.html
http://www.nlm.nih.gov/medlineplus/ency/article/000528.htm
http://en.wikipedia.org/wiki/Glucose-6-phosphate_dehydrogenase_deficiency
http://www.uic.edu/pharmacy/services/di/G6PD.htm
http://www.g6pd.org
http://www.medicinenet.com/g6pd_deficiency/article.htm
