Thalassemia is a genetic disorder that is due to mutations of the genes that are responsible for the production of hemoglobin in the blood.
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As one of the most common autosomal recessive disorders in the world, thalessemia affects about 1 in every 100,000 individuals. The genetic prevalence of this condition varies greatly according to the region of the world, as well as the specific ancestry of an individual.
There are two broad types of thalassemia including alpha-thalassemia and beta-thalassemia, each of which has a different prevalence among certain ethnicities or population groups.
Inheritance Pattern
Both alpha- and beta-thalassemia are generally inherited in an autosomal recessive pattern. This means that males and females are affected equally by thalessemia, as it does not involve the sex chromosome. In order for a child to be born with thalessemia, both parents must be carriers of a gene mutation, but do not necessarily need to have the disease. This is because the presence of two gene mutations, each of which are aqcuired from each parent, allows for the trait to develop and become evident.
If both parents carry a gene mutation, there is a 25% chance that any one of their children will be affected by thalessemia. The risk increases if one or more parent possesses additional gene mutations, as it becomes more likely that the defected gene will be inherited.
Rare cases of thalassemia being inherited in a dominant pattern have also been reported. In these cases, only one parent carrying the gene mutation still has a child with the genetic disorder. Nevertheless, this is a rare occurrence; therefore, the condition more commonly follows an autosomal recessive pattern.
What is Thalassemia? Types, Treatment and Symptoms
Alpha-Thalassemia
The region of the world and ethnicity of the individual is an important factor in the prevalence of the gene mutations. To this end, alpha-thalassemia is more common in Southeast Asia than in other areas of the world, although anyone may be affected by the gene mutation that leads to this condition.
The following list summarizes which population groups are more likely to be affected by alpha-thalassemia.
- Southeast Asia: The thalassemia trait is present in 1-30% of the population, with up to 40% of the population suspected to be genetic carriers.
- Sub-Saharan Africa: The thalassemia trait is present in 0% of the population, with up to 50% of the population suspected to be genetic carriers.
- Western Pacific: The thalassemia trait is present in 0% of the population, with up to 60% of the population suspected to be genetic carriers.
- Eastern Mediterranean: The thalassemia trait is present in 0-2% of the population, with up to 60% of the population suspected to be genetic carriers.
- Americas: The thalassemia trait is present in 0-5% of the population, with up to 40% of the population suspected to be genetic carriers.
- Europe: The thalassemia trait is present in 1-2% of the population, with up to 12% of the population suspected to be genetic carriers.
Beta-Thalassemia
People with origins in the Mediterranean, as well as both African and South Asian areas, are more likely to be affected by beta-thalassemia.
The estimated prevalence of those affected by the genetic mutations responsible for beta-thalessemia throughout the world includes:
- Eastern Mediterranean: 2-18%
- Europe: 0-19%
- Western Pacific: 0-13%
- Sub-Saharan Africa: 0-12%
- Southeast Asia: 0-11%
- Americas: 0-3%
Gene Carriers
It is important for individuals who are known to carry gene mutations that may lead to thalassemia to seek medical advice before deciding to have children. This is because it is possible for future children to inherit the defective gene, particularly if both parents are carriers, regardless of the presence of symptoms.
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