Favism: Do Both Parents Need to Be Carriers for Females?

Favism, also known as fava bean disease, is a genetic disorder characterized by a deficiency of the enzyme glucose-6-phosphate dehydrogen

To develop favism, a female must inherit the gene from both parents, meaning both parents need to be carriers of the gene.

ning, 20~29 year old female. Ask Date: 2008/05/26

Dr. Jian Yingxiu reply Rare Disease

The gene for G6PD deficiency (Favism) is located on the X chromosome.
Females inherit one X chromosome from each parent, and if either of these contains a pathogenic mutation, there is a chance of developing enzyme deficiency (Favism).
However, because females have another normal X chromosome, their bodies may sometimes express one X chromosome while not expressing the other.
As a result, the enzyme activity in carrier females can range from very low to normal.

Reply Date: 2008/05/26

More Info

Favism, or G6PD deficiency, is a genetic condition that affects the enzyme glucose-6-phosphate dehydrogenase (G6PD), which plays a crucial role in protecting red blood cells from damage. This condition is particularly relevant in certain populations and can lead to hemolytic anemia when individuals consume fava beans or are exposed to certain medications or infections.

To understand whether both parents need to be carriers for a female to inherit G6PD deficiency, it's essential to delve into the genetics of the condition. G6PD deficiency is an X-linked recessive disorder. This means that the gene responsible for the condition is located on the X chromosome. Males have one X and one Y chromosome (XY), while females have two X chromosomes (XX).

For a female to be affected by G6PD deficiency, she must inherit two copies of the mutated gene—one from each parent. If her father has G6PD deficiency, he will pass on his Y chromosome to his sons and his X chromosome (which carries the deficiency) to his daughters. Therefore, if a father is affected, all of his daughters will be carriers of the condition, but they will not be affected unless their mother is also a carrier or affected.

If the mother is a carrier (meaning she has one normal X chromosome and one mutated X chromosome), there is a 50% chance that she will pass on the mutated gene to her daughters. If both parents are carriers, there is a 25% chance that a daughter will inherit the condition (receiving the mutated gene from both parents), a 50% chance that she will be a carrier (receiving the mutated gene from one parent), and a 25% chance that she will inherit two normal genes.

In summary, for a female to be affected by G6PD deficiency, she must inherit the mutated gene from both parents. If only one parent is a carrier, the daughter will be a carrier but not affected. This genetic mechanism highlights the importance of family history and genetic counseling for families with a known history of G6PD deficiency.

In terms of management and awareness, it is crucial for families to understand the implications of G6PD deficiency. Carriers often do not exhibit symptoms, but they can pass the gene to their offspring. Genetic testing can be beneficial for individuals with a family history of G6PD deficiency, especially before planning a family.
Additionally, awareness of the condition is essential for preventing hemolytic crises. Individuals with G6PD deficiency should avoid certain foods, like fava beans, and be cautious with medications that can trigger hemolysis. Regular check-ups and consultations with healthcare providers can help manage the condition effectively.

In conclusion, while both parents do not need to be carriers for a female to inherit G6PD deficiency, understanding the genetic transmission of the condition is vital for informed family planning and management of the disorder.

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