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 one 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 often in persons from Southeast Asia, the Middle East, China, and in those of African descent.
Beta thalassemias occur most often in persons of Mediterranean origin. To a lesser extent, Chinese, other Asians, and African Americans can be affected.
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 gene defect from both parents to develop thalassemia major.
Thalassemia minor occurs if you receive the faulty gene from only one parent. Persons with this form of the disorder are carriers of the disease. Most of the time, they 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