How is alpha-thalassemia inherited?

The inheritance of alpha-thalassemia is complex because the condition involves two genes: HBA1 and HBA2. People have two copies of the HBA1 gene and two copies of the HBA2 gene in each cell. Each copy is called an allele. Therefore, there are 4 alleles that produce alpha-globin, the protein that results from these genes. For each of the 2 genes, one allele is inherited from a person's father, and the other is inherited from a person's mother - so each person inherits 2 alleles from each parent. The different types of alpha- thalassemia result from the loss of some or all of these alleles.

If both parents are missing at least one alpha-globin allele, each of their children are at risk of having Hb Bart syndrome or hydrops fetalis, hemoglobin H (HbH) disease, or alpha-thalassemia trait. The precise risk depends on how many alleles are missing and which combination of the HBA1 and HBA2 genes is affected.

In most cases:

  • a person with 1 mutated allele is a carrier and has no signs or symptoms
  • a person with 2 mutated alleles may have mild signs or symptoms of alpha-thalassemia (called alpha-thalassemia minor, or alpha-thalassemia trait)
  • a person with 3 mutated alleles has moderate to severe symptoms (called HbH disease)

When there are 4 mutated alleles, the condition is called alpha-thalassemia major or hydrops fetalis. In these cases, an affected fetus usually does not survive to birth, or an affected newborn does not survive long after birth.

Last updated on 05-01-20

How might alpha-thalassemia be treated?

Treatment of alpha-thalassemia often includes blood transfusions to provide healthy blood cells that have normal hemoglobin. Bone marrow transplant has helped to cure a small number of individuals with severe alpha- thalassemia.

Last updated on 05-01-20

Name: Cooley's Anemia Foundation 330 Seventh Avenue, Suite 200
New York, NY, 10001, United States
Phone: 212-279-8090 Fax : 212-279-5999 Email: Url:
Name: Thalassaemia International Federation PO Box 28807 Nicosia 2083
Phone: 22 319129 Fax : 22 314552 Email: Url:
Name: European Network for Rare and Congenital Anaemias (ENERCA) University of Barcelona Red Cell Pathology Unit
C/Villarroel, 170 - 08036 Barcelona
Phone: (34) 93 451 5950 Fax : (34) 93 227 1764 Email: Url:
Name: March of Dimes 1275 Mamaroneck Avenue
White Plains, NY, 10605, United States
Phone: 914-997-4488 Toll Free: 888-663-4637 Fax : 914-997-4763 Email: Url:

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