Alternative Names
Erythroblastic Anemia; Mediterranean Anemia; thalassemia, beta type; beta-thal; betaglobinopathy; hemoglobinopathy
Symptoms & Characteristics
Thalassemia is genetic condition that involves abnormalities in hemoglobin (the molecule in red blood cells that transports oxygen throughout the body) which may lead to an ineffective production or increased destruction of red blood cells as well as reduced oxygen transport. Hemoglobin is mostly made up of two types of proteins (or chains), called alpha and beta globin. Defects in these proteins cause alpha-thalassemia and beta-thalassemia, respectively.
There are (at least) three main types of beta-thalassemia with symptoms that range from mild to severe. Beta-globin is produced by two genes, one gene from each parent. The severity of the condition correlates with the amount of normal beta-globin production. Here are the three main types:
- Beta thalassemia minor is when a person has one mutation and is a carrier. These people typically do not have any symptoms, but may have a mild anemia and other changes in blood.
- Thalassemia intermedia is when a person has reduced beta-globin production, which is caused by two mutations. Affected people typically have a mild to moderate anemia, although symptoms may be more severe. Regular treatment is needed.
- Thalassemia major is when a person has no beta-globin production, which is caused by two mutations. Untreated, affected people typically have severe symptoms including, failure to thrive, yellowing of the eyes and skin (called jaundice), enlarged spleen and liver, brittle and abnormal bones, recurrent infections, and heart problems, which appear within the first year or two of life. Regular treatment is needed.
Other types of beta-thalassemia include (but are not limited to):
- Some people have a variant form of beta-hemoglobin called hemoglobin E. These people are typically healthy or only have a mild anemia, unless they have beta-thalassemia as well. Such combination of hemoglobin E and beta-thalassemia leads to a more severe condition, called E/-beta-thalassemia. Affected people typically have mild to severe anemia, which may resemble beta-thalassemia intermedia or major.
- Some people have one gene for beta-thalassemia and one gene for sickle cell disease. Then they have what is called sickle cell/beta-thalassemia. Affected people typically have symptoms that resemble sickle cell disease, including varying degrees of anemia, recurrent infections, pain, and organ damage.
Treatment
Early diagnosis, routine surveillance and treatment of beta-thalassemia may help to manage some of the symptoms and sometimes prevent related problems.
How Common Is It?
Beta-thalassemia is most common in people of Mediterranean (i.e. Greek and Italian), Middle Eastern, Southeast Asian, southern Chinese and African descent.
- Hemoglobin E is the most common abnormal variant of beta-hemoglobin in the world. E/-beta-thalassemia is most common in people of Cambodian, Vietnamese, Thai and Laotian ancestry.
Genetics & Inheritance
Beta-thalassemia is caused by mutations in the HBB gene on the chromosome 11 at the location p15.5.
Over 200 mutations in the HBB gene have been found. We all have two copies of almost every gene – one from each parent. It is necessary to have two mutations, one from each parent, to be affected with each of these types of beta-thalassemia. This is called autosomal recessive inheritance.
- Both parents of an affected person are always both obligate carriers (each have only one mutation). Two carriers have a 25% chance with each pregnancy to have an affected child.
- Without a family history, the chance to be a carrier is determined by a person's ethnic background.
There are many genetic and non-genetic conditions, which have symptoms that overlap with beta-thalassemia. A genetic consultation with a trained genetic professional is important for a complete evaluation, accurate diagnosis, as well as discussion of the benefits and limitations of testing and recurrence risk.
Genetic Testing
Clinical genetic testing for beta-thalassemia can be broken down into two categories: diagnostic testing and carrier testing.
- Diagnostic testing may be used to confirm or rule out a diagnosis in a person suspected to have beta-thalassemia.
- Carrier testing for beta-thalassemia is available for people of high risk ethnic groups.
Clinical genetic testing for beta-thalassmia is available online (over the internet) or through an in person genetic consultation. Go to the Tests tab to link to the best providers, compare providers and read provider reviews. Use our find a genetic professional directory to locate a trained genetic professional in your area.
Support & More Information
More information can be found at:
Support can be found at: