Beta thalassemia is a common genetic disorder affecting the production of hemoglobin, a protein found in red blood cells. When working normally, hemoglobin transports oxygen from the lungs to the body’s tissues. People with beta thalassemia have reduced hemoglobin, meaning their cells get less oxygen.
This lack of oxygen causes the signs and symptoms of beta thalassemia. Affected people have anemia, which means they have fewer red blood cells than normal, varying in severity from mild to life-threatening. Currently beta thalassemia cannot be reversed, and is treated with blood transfusions.
Types of Beta Thalassemia and Symptoms
The two types of beta thalassemia are as follows:
- Beta thalassemia major (also called Cooley’s Anemia) — this is the most severe form, manifesting early in childhood. Signs and symptoms include failure to thrive, enlarged organs and severe anemia.
- Beta thalassemia intermedia — this is the less severe form, which can appear in childhood or later. Signs and symptoms include milder anemia and bone abnormalities.
The Gene Involved in Beta Thalassemia
Beta thalassemia is the result of mutations in a gene called hemoglobin, beta (HBB), located on chromosome 11. HBB codes for the beta-globin protein, which plays an important role in the making of hemoglobin. Mutations lead to a reduction in the amount of hemoglobin made, resulting in the signs and symptoms of beta thalassemia.
Inheritance of Beta Thalassemia
Beta thalassemia is usually autosomal recessive. This means an affected person will have two mutated gene copies in each somatic (body) cell — one inherited from the mother, the other from the father. Those with only one mutated gene copy in each cell have 'beta thalassemia minor'. They will not experience the typical signs and symptoms of the disorder, but they will sometimes have mild anemia.
When both parents have beta thalassemia minor, the chances of having a child with the disorder are the following for each pregnancy:
- A 1 in 4 (25%) chance of having a child affected with beta thalassemia.
- A 1 in 2 (50%) chance of having a child who is a carrier of beta thalassemia (beta thalassemia minor).
- A 1 in 4 (25%) chance of having a child who is completely unaffected.
Genetic Testing and Beta Thalassemia
Beta thalassemia and beta thalassemia minor can be detected with blood tests, and prenatal testing is also possible. Genetic counseling may be an option for those seeking support and information on genetic disorders.
Visit the Cooley’s Anemia Foundation and Thalassemia Support Foundation websites for more information on beta thalassemia. For more details on seeking genetic testing, read Understanding Genetic Testing in Healthcare and Understanding Genetic Consultation.
Sources
“Beta-Thalassemia”, updated: 17th June 2010, GeneReviews (NCBI Bookshelf) website, accessed: 1st December 2010, authors: Cao, Antonio; Galanello, Renzo.
“Beta thalassemia”, reviewed: July 2009, Genetics Home Reference website, accessed: 1st December 2010, no author specified.
“Thalassemia”, Genes and Disease (NCBI Bookshelf) website, accessed: 1st December 2010, no author specified.
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