Why people have
G6PD
The defect is sex-linked, transmitted from mother (usually a healthy carrier) to son (or daughter, who would be a healthy carrier too; This is due to the fact that the structure of G-6-PD is carried on the X chromosome
What is G6PD deficiency?
Glucose-6-Phosphate Dehydrogenase (G6PD) is an enzyme which protects the red blood cells and prevents them from being damaged. People with G6PD deficiency can generally enjoy normal health. However, if they suffer from a severe infection or are exposed to oxidant stress such as from certain drugs or chemicals, massive damage of red blood cells may occur, leading to acute hemolysis. Bilirubin will be produced as red blood cells are broken down during acute hemolysis, resulting in jaundice. If newborn babies with severe jaundice do not receive timely treatment, excessive bilirubin may accumulate in the brain, causing irreversible damage to the brain, a condition clinically known as kernicterus. It may result in hearing loss, intellectual disability, spasticity or even death.
G6PD deficiency is common in Hong Kong. According to the statistical data from the Neonatal Screening Programme, there are 4 to 5 out of 100 male newborns and 3 to 5 out of 1,000 female newborns suffering from G6PD deficiency.
How Common is G6PD?
Why the majority of people with G6PD deficiency are male?
G6PD deficiency is a genetic condition with X-linked recessive inheritance. 2 In human, each cell contains 23 pairs (46 chromosomes) of chromosomes. The 23rd pair are the sex chromosomes. Males have one X and one Y chromosome (XY). Females have two X chromosomes (XX). The gene coding for G6PD enzyme is located on the X chromosome. As males have only one X chromosome and thus one copy of G6PD gene, they would have G6PD deficiency if the G6PD gene carries a mutation. The G6PD activity in the blood will be reduced. A female who has a mutant G6PD gene on one of her X chromosomes is a carrier for G6PD deficiency. She usually has a normal copy of G6PD gene on the other X chromosome that Sex chromosome 3 produces sufficient G6PD to protect the red blood cells. Therefore, she may not present any symptoms of G6PD deficiency. Female carriers for G6PD deficiency have 50% chance to pass on the mutated gene to their next generation. Each son has 50% chance of inheriting the mutant gene and thus suffers from G6PD deficiency. Each daughter has 50% chance of inheriting the mutant gene and thus becomes a carrier of G6PD deficiency.