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Genetic and Rare Diseases Information Center (GARD)

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Other Names for this Disease
  • Beta thalassemia intermedia
  • Beta thalassemia major
  • Beta thalassemia minor
  • Cooley's anemia
  • Erythroblastic anemia
More Names
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What is beta-thalassemia?

How is beta-thalassemia inherited?

What is beta-thalassemia?

Beta-thalassemia is a blood disorder that reduces the production of hemoglobin. Without sufficient hemoglobin, red blood cells do not develop normally, causing a shortage of mature red blood cells, leading to anemia and other health problems. Severe beta-thalassemia is called “thalassemia major” or “Cooley’s anemia.” Thalassemia intermedia is the less severe form. Mutations in the HBB gene cause beta-thalassemia. This condition is usually inherited in an autosomal recessive fashion, which means people with beta thalassemia have mutations in both of their HBB genes. People who have only one HBB mutation may have no symptoms or develop mild symptoms; these individuals are said to have thalassemia minor.[1]
Last updated: 7/7/2011

How is beta-thalassemia inherited?

Beta-thalassemia major and beta-thalassemia intermedia are usually inherited in an autosomal recessive pattern, which means both copies of the HBB gene in each cell have mutations. The parents of an individual with an autosomal recessive condition each carry one copy of the mutated gene (referred to as carriers), but they typically do not show signs and symptoms of the condition. When two people who are carriers of an autosomal recessive condition have a child, there is a 25% (1 in 4) chance that the child will have the condition, a 50% (1 in 2) chance that the child will be a carrier like each of the parents, and a 25% (1 in 4) chance that the child will not have the condition and not be a carrier.[1]

Sometimes, people with only one HBB gene mutation in each cell (carriers) develop mild anemia. These people are said to have beta-thalassemia minor or beta-thalassemia trait. Therefore, each time two individuals with beta-thalassemia minor have a child, there is a 25% chance that each child will have either beta-thalassemia major or intermedia (depending on the severity of that child's symptoms), a 50% chance that the child will be a carrier without symptoms or have beta-thalassemia minor (depending on whether the child has anemia), and a 25% chance that the child will not have beta-thalassemia and not be a carrier for the condition.[1]

In a small percentage of families, the HBB gene mutation is inherited in an autosomal dominant manner. In these cases, one copy of the altered gene in each cell is enough to cause the signs and symptoms of beta-thalassemia.[1]
Last updated: 7/7/2011

  1. Beta thalassemia. Genetics Home Reference. July 2009; Accessed 7/7/2011.