Definition of Thalassemia:

Thalassemia is an blood disorder passed down through families (inherited) in which the body makes an abnormal form of hemoglobin, the protein in red blood cells that carries oxygen. The disorder results in excessive destruction of red blood cells and anemia.

See also:

• Hemolytic anemia
• Sickle cell disease

Causes, incidence, and risk factors:

Hemoglobin is made of two proteins: Alpha globin and beta globin. Thalassemia occurs when there is a defect in a gene that helps control production of these proteins.

There are two main types of thalassemia:

• Alpha thalassemia occurs when a gene or genes related to the alpha globin protein are missing or changed (mutated).
• Beta thalassemia occurs when similar gene defects affect production of the beta globin protein.

Alpha thalassemias occur most commonly in persons from southeast Asia, the Middle East, China, and in those of African descent.

Beta thalassemias occur in persons of Mediterranean origin, and to a lesser extent, Chinese, other Asians, and African Americans.

There are many forms of thalassemia. Each type has many different subtypes. Both alpha and beta thalassemia include the following two forms:

• Thalassemia major
• Thalassemia minor

You must inherit the defective gene from both parents to develop thalassemia major.

Thalassemia minor occurs if you receive the defective gene from only one parent. Persons with this form of the disorder are carriers of the disease and do not have symptoms.

Beta thalassemia major is also called Cooley's anemia.

Risk factors for thalassemia include:

• Asian, Chinese, Mediterranean, or African American ethnicity
• Family history of the disorder