Glucose-6-phosphate dehydrogenase (g6pd) Deficiency
Overview
G6PD
deficiency is an X-linked inherited blood disorder in which the body
doesn’t have enough of the enzyme G6PD. This means that if a boy (XY)
receives an X chromosome that is deficient, he will have a significant
G6PD deficiency. A girl (XX) can receive either one deficient X
chromosome, or two. This means that girls can have more varied levels
of G6PD deficiency, from non-symptomatic to highly deficient. Even some
girls who are carriers (one good X and one bad X) have been found to be
symptomatic. Some females are more highly deficient than expected,
because they have one deficient X chromosome and a second mutated and/or
damaged X chromosome.
- This is the most common inherited enzyme defect in the world.
- With the right precautions, a child with G6PD deficiency can lead a healthy and active life.
- G6PD
deficiency is common in Guangdong, Taiwan, Guangxi and other parts of
South China. It is found in the Han, Zhuang, Li and Miao ethnic groups,
as well as others.
- In China many of those affected with G6PD
deficiency have less than 10% enzyme activity, resulting in a high
degree of sensitivity to oxidizing substances.
- Some of the G6PD variants result in chronic hemolytic anemia (CNSHA).
- G6PD
deficiency is thought to be a defense against Malaria and occurs in the
same regions as the Thalassemias. A person can have both Thalassemia,
major or trait and G6PD deficiency.
- Tests for G6pd deficiency in boys are easily administered and reliable.
- Tests
for G6pd deficiency in girls are difficult, expensive and often require
genetic analysis. However in China new more reliable, less expensive
tests are being developed to detect G6PD deficiency in girls.
- G6PD deficiency in women has been found to become more acute as they age.
- Those
who are G6PD deficient are likely to have an increased risk of
diabetes, hypertension, sepsis and its complications and cataracts.
G6PD
is required to neutralize oxidative substances in the body and
metabolize carbohydrates properly. Without enough G6PD, red blood cells
begin to break down quickly. G6PD is important for the life of all
cells, cell growth and development. G6pd deficiency is not curable at
this time. The only treatment is avoidance of trigger substances and
hospitalization and blood transfusions in cases of extreme hemolysis
(breakdown of red blood cells). Extreme haemolytic episodes can result
in renal failure and/or death.
Things to avoid
Each
person, and each G6PD variant (approximately 400) can react differently
to identified trigger substances. There are however,
accepted lists of substances that may need to be avoided.
These include:
- NSAIDS (Asprin, Ibuprophen)
- Tylenol
- Quinolones
- Drugs metabolized through the liver or known to cause blood or liver related problems or hemolysis
- Sulfa drugs
- Petrochemically
derived substances (This is a long list and gets longer every year.
Many artificial foods, dyes and vitamins are included in this list.)
- Moth Balls and anything containing naphthalene.
- Methylene and Toluidine blue
- Legumes and their derivatives (for example: soy, peanut, beans, peas, licorice, food thickeners and gums, MSG)
- Other
substances including blueberries, blue food coloring, tonic
water/quinine, red wine, sulfites, mothballs, and petroleum derived
substances.
- Illness / fever can also trigger G6PD symptoms.
Some
G6PD deficient people try to reduce oxidative stress by ingesting
antioxidants (w/o blueberries or blue food coloring) and taking folic
acid, in addition to avoiding trigger substances.
Symptoms
Symptoms
can be found in both those who have been diagnosed (boys and some
girls) and those who have not yet been diagnosed (esp. in girls from
South China / SE Asia). Symptoms generally occur within three days of
exposure to triggering substance. Once the triggering substance is
removed or the illness resolved, the symptoms generally improve over a
period of weeks. Mild symptoms can be treated at home, more severe
symptoms may require hospitalization.
- paleness (in darker-skinned children paleness is sometimes best seen in the mouth, especially on the lips or tongue)
- extreme tiredness
- rapid heartbeat
- rapid breathing or shortness of breath
- an enlarged spleen
- dark, tea-colored urine
- abdominal / back pain
- bruising
- fever
- weakness
- dizziness
- confusion
Classes of G6PD Enzyme Variants:
| Class | Level of deficiency | Enzyme activity | Prevalence |
I
|
Severe
|
Chronic nonspherocytic hemolytic anemia in the presence of normal erythrocyte function
|
Uncommon; occurs across populations
|
II
|
Severe
|
Less than 10 percent of normal
|
Varies; more common in Asian and Mediterranean populations
|
III
|
Moderate
|
10 to 60 percent of normal
|
10 percent of black males in the United States
|
IV
|
Mild to none
|
60 to 150 percent of normal
|
Rare
|
V
|
None
|
Greater than 150 percent of normal
|
Rare
|
Resources
• www.g6pddeficiency.org
• www.rialto.com
• www.g6pd.org
• www.ghr.nlm.nih.gov
• www.nlm.nih.gov/medlineplus/ency/article/000528.htm
• memo.cgu.edu.tw/cgmj/2809/280902.pdf
• www.hkcpath.org/docs/Topical%20Update/Topical%20Update%20V2I1.pdf
• www.aafp.org/afp/2005/1001/p1277.html
• www.bioinf.org.uk/g6pd/
•
Hirono A, Fujii H, Miwa S. Identification of two novel deletion
mutations in glucose-6-phosphate dehydrogenase gene causing hemolytic
anemia. Blood 1995;85:1118-21.
• Mason PJ, Sonati MF, MacDonald D, et
al. New glucose-6-phosphate dehydrogenase mutations associated with
chronic anemia. Blood 1995;85:1377-80.
