Beta thalassemia patients demonstrate an inherited defect in beta globin chain production. Since there are two gene loci coding for beta chain production on chromosome 11, there are different forms of beta thalassemia depending on whether one or both loci have been fully or partially deleted. The greater the number of loci deleted or inactivated, the greater the severity of the anemia which develops.
Many different mutations exist that result from partial deletions of beta genes. This unit of study deals only with the forms of beta thalassemia that have entire loci deleted. In addition, it is important to note that deletions of other globin genes coded for on chromosome 11 can result in combinations as delta-beta thalassemia.
There are certain regions of the world where severe forms of beta thalassemia occur more frequently. These include: northern Italy, Algeria, Greece, Saudi Arabia, and southeast Asia. Individuals descending from Africa have a higher frequency of inheriting milder forms of beta thalassemia compared to the average frequencies noted elsewhere.