The Genetics & Demographics of Thalassemia

Genetics 101

Having a basic understanding of genetics is invaluable in trying to understand the complexities of thalassemia and its inheritance. Genetics is the study of genes, which are most simply explained as biological instructions. Thousands of genes are passed onto each of us from our mother through the egg and our father through the sperm. These genes instruct our bodies to grow and develop, determining everything from our sex to the color of our eyes and the shapes of our noses.


A complete copy of all the genetic material necessary to create a human being is contained in most all of our body's cells. This genetic material is packaged onto structures called chromosomes. A complete "genetic blueprint" consists of 23 pairs of chromosomes (46 total). Chromosomes are themselves made up of a chemical strand called DNA. Along each DNA strand there are many genes. Each gene is an instruction for making a particular protein. Proteins are responsible for carrying out all the tasks needed to create and maintain a living person. In thalassemia, a change occurs in the genes that tell the body how to make the globin protein, which makes up part of hemoglobin, the oxygen-carrying component inside our red blood cells. This genetic change leads to decreased or absent production of this very important protein.


There are two main types of thalassemia trait: alpha thalassemia trait and beta thalassemia trait. Individuals who have beta thalassemia trait have one normal beta globin gene and one that is altered such that it makes little or no beta globin. There are subtypes of alpha thalassemia trait. Individuals with 'silent alpha thalassemia trait' are missing one alpha globin gene. When two alpha globin genes are missing, an individual is said to have 'alpha thalassemia trait'. This can occur in two different ways. The 'cis' type of alpha thalassemia trait occurs when the two genes are missing from the same chromosome. This type is most common in those of Southeast Asian, Chinese, or Mediterranean ancestry. The 'trans' type of alpha thalassemia trait occurs when the two genes are missing from different chromosomes. This type is most common in African Americans.

Worldwide prevalence and demographics

Thalassemia occurs across the globe, but is most prevalent among people from the following countries:

  • Africans - mostly central and western countries
  • Albania
  • Armenia
  • Azerbaijan
  • Bahrain
  • Bulgaria
  • Burma
  • Cambodia
  • China
  • Cyprus
  • Egyptian
  • Georgia
  • Greece
  • India
  • Indonesia
  • Iran
  • Italy
  • Laos
  • Malaysia
  • Pakistan
  • Phillipines
  • Romania
  • Sardinia
  • Saudi Arabi
  • Singapore
  • Thailand
  • VietnamĀ