G6PD enzyme deficiency causes jaundice

Donya Betancourt, Pediatrician, drdonya@hotmail.com

The most common human enzyme deficiency, which causes jaundice in newborns, in the world is G6PD enzyme deficiency.

G6PD, or Glucose-6-Phosphate Dehydrogenase, deficiency is the lack of glucose-6-phosphate dehydrogenase, an enzyme present in red blood cells.

Typically when a person has G6PD deficiency, the two major pathologies associated with it are hemolytic anemia and prolonged neonatal jaundice.

In G6PD deficient individuals, anemia is usually caused by certain oxidative drugs, infections or fava beans.

Red blood cells carry oxygen in the body and G6PD protects these cells from natural oxygen chemicals that may build up when you have a fever or take certain medications. If there are too many of these chemicals, they can destroy the red blood cells.

When the red blood cells can no longer transport oxygen effectively throughout the body; a condition called hemolytic anemia arises. In addition to hemolytic anemia, G6PD deficient individuals can expect several other clinical manifestations of their condition including neonatal jaundice, abdominal and/or back pains, dizziness, headaches, dyspnea (irregular breathing) however Neonatal jaundice and hemolytic anemia are the two major pathologies associated with G6PD deficiency.

G6PD deficiency is inherited by a gene on the X chromosome. Chromosomes are the structures in our cells which contain our genes; the gene codes determine all of our physical traits such as eye color and blood type. In humans, we have 46 chromosomes, or 23 pairs; the last pair is the X and Y chromosome (also known as the sex chromosomes) which among other things determines what sex an individual will be.

Females have two X-chromosomes, while males have one X and one Y chromosome. The X-chromosome is especially important because it carries genes that are critical to human survival.

An important gene located on the X-chromosome is the gene for the G6PD enzyme. Any gene located on the X-chromosome is called an X-linked gene.

G6PD deficiency is inherited from females who carry one copy of the gene on one of their X chromosomes. Sons who receive the gene have G6PD deficiency, and daughters who receive the gene are carriers (who generally do not show any symptoms). Sons and daughters who do not receive the gene are unaffected.

G6PD deficiency will only manifest itself in females when there are two defective copies of the gene in the genome. When a certain heritable trait is expressed in such a manner, it is a called a recessive trait.

In males, however, where there is only one X-chromosome, one defective G6PD gene is sufficient to cause G6PD deficiency. All X-linked genetic conditions, such as G6PD deficiency, are more likely to affect males than females.

With regards to the demographics of G6PD deficiency, most of the affected individuals reside in Africa, the Middle East, and Southeast Asia.

African-Americans and some isolated tribes in Africa and Southeast Asia exhibit the highest frequency of incidence for any given population; a defective enzyme can be found in as many as one in four people among these populations.

Hemolytic anemia is a disorder in which the red blood cells are destroyed faster than the bone marrow can produce them.

What are the symptoms of hemolytic anemia? The following are the most common symptoms of hemolytic anemia. However, each individual may experience symptoms differently.

Symptoms may include abnormal paleness or lack of color of the skin, jaundice, or yellowing of the skin, eyes, and mouth, dark color urine, fever, weakness, dizziness, confusion, intolerance to physical activity, enlargement of the spleen and liver or increased heart rate.

Because certain medicines can cause natural oxygen chemicals to build up in the body persons with G6PD deficiency cannot protect their red blood cells against the buildup of oxygen chemicals, and the blood cells are destroyed, causing anemia. Therefore, persons with G6PD deficiency need to avoid exposing themselves to certain medicines, such as aspirin (acetylsalicylic acid), certain antibiotics used to treat infections, fava beans, and moth balls.

G6PD deficiency can be diagnosed by a simple blood test and as matter of common practice the test is run on all new born babies who display the symptoms of jaundice.