Carrier rate:
Up to 1 in 30 in individuals of Mediterranean descent (mainly Greek and Italian); 20% of Kurdish Jews, 10% of Iranians, 2% to 4% in Middle Eastern and North African Jews

Disease frequency:
Approximately 1 in 3,600 for individuals of Mediterranean (mainly Greek, Italian and Spanish) and Middle Eastern descent.

Other ethnic groups in which it occurs:
May occur in all ethnic groups.

Inheritance:
Autosomal recessive

Age of onset of symptoms:
Thalassemia major generally presents in the first two years of life with severe anemia and enlargement of the liver and/or spleen. Thalassemia intermedia presents at a later age with milder anemia.

Symptoms:
Anemia is the main feature of beta thalassemia. Thalassemia major generally presents in the first two years of life with severe anemia and enlargement of the liver and/or spleen. These children often have poor growth, paleness, irritability, fever, feeding problems, failure to thrive, impaired physical capacity, iron overload and possible bone abnormalities. Puberty may also be delayed. Thalassemia intermedia presents at a later age with milder anemia. Affected individuals may also have some features of thalassemia major, such as enlarged liver and/or spleen, iron overload and bony abnormalities. Carriers of the beta thalassemia trait (one mutation) may have mild anemia.

Average lifespan:
The severity of the anemia is the greatest factor. Untreated, individuals with beta thalassemia major may die before the third decade, but milder cases can allow for a normal lifespan.

What causes the features of the disease:
Red blood cells rely on the protein hemoglobin to transport oxygen from the lungs to the rest of the body. When genetic mutations prevent the production of the beta chain, one of two structures necessary to complete a hemoglobin protein, red blood cells aren't produced in sufficient quantities, leading to anemia. Beta thalassemia is the most common inherited single gene disorder in the world. This disorder covers a spectrum of anemias, ranging in severity from mild (intermedia) to severe (thalassemia major or Cooley's anemia). Individuals with thalassemia intermedia have some residual beta chain production, whereas those with thalassemia major have none. Beta thalassemia is most frequently seen in humid climates with a high incidence of malaria, such as Africa, the Mediterranean, the Middle East and Asia. This is due to the fact that being a carrier is thought to confer some resistance to malaria.

Treatment or management:
Bone marrow transplants and regular blood transfusions have both proven successful, depending on the severity of the anemia. Individuals with thalassemia intermedia generally do not need transfusions as frequently, if at all. Chelation therapy, which removes excess iron from the blood stream, may also be necessary to prevent iron overload.

Carrier testing - number of mutations screened for and detection rate:
Blood tests to assess for red blood cell and hemoglobin abnormalities can be used to determine carrier status. If abnormal, genetic testing can be performed of the HBB gene, which can identify up to 99% of carriers.

Other testing information:
Testing is available to those with a previously affected child or to couples found to be at risk as carriers. To assist in making the diagnosis a physician knowledgeable of the symptoms can order blood tests to assess for red blood cell and hemoglobin abnormalities. If abnormal, genetic testing for mutations on the HBB gene can be performed.

Current research:
There are investigational agents known to increase Hb F level as well as gene therapy options that are currently being studied.

For more information:
Cooley's Anemia Foundation:
   www.thalassemia.org
Thalassemia International Federation:
   www.thalassaemia.org.cy
Northern California's Comprehensive Thalassemia Care:
   www.thalassemia.com