Thalassaemia

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Heamoglobin is made of alpha and beta globin subunits, which are transcribed by genes on our chromosomes. If two of the genes on our chromosomes that code for beta globins or three of the genes on our chromosomes that code for alpha globins are missing or abnormal, it leads to a plunge in globin production and thus, thalassemia. The plunge in globin production, when severe, causes the red blood cells in the body to form abnormally, making it difficult for them to bind sufficient amounts of oxygen.

Thalassemia is a very complex, inherited disease. Since the plunge in globin production characteristic in thalassemia is dependent upon mutations in the process of transcribing the genes necessary for globin production, thalassemia is an extremely variable disease and can affect people in many different forms.

The disease can be categorized into two main subgroups: alpha thalassemia and beta thalassemia.

Alpha Thalassemia

There are four alpha globin genes in a normal human being without Thalassemia. When two of these genes on a chromosome are missing or abnormal, it causes alpha-0 thalassemia (it is names such because there is 0 alpha globin production from this chromosome). When only one alpha globin gene on one of the chromosomes is missing or abnormal, there is still alpha globin production from both of the chromosomes (although it will be less in the chromosome without the two alpha globin genes) and thus, this form of alpha thalassemia is known as alpha-plus thalassemia.

Beta Thalassemia

The different forms of beta thalassemia are names in the same way as the different forms of alpha thalassemia: when both of the genes encoding beta globin proteins are missing/abnormal, it causes beta-0 thalassemia and when one gene encoding beta globin proteins in missing/abnormal on one of the chromosomes, it is known as beta-plus thalassemia. Beta-thalassemia is only expressed entirely after birth since beta-chains are only fully activated after birth[1]. Patients with Beta-thalassemia often have abnormally high levels of iron, which could potentially lead to organ damage. Without iron chelation therapy almost all β-thalassaemia patients will accumulate potentially fatal iron levels. Iron chelation therapy is a drug based therapy which aims to eliminate excess iron from the body[2].

References

  1. Clegg, J.B. and Weatherall, D.J. (2001). The Thalassemia Syndromes. 4th ed. Massachusetts: Blackwell Science Ltd. p. 121-133.
  2. Astrid Sigel, Helmut Sigel and Roland K. O. Sigel.(2013). Interrelations between Essential Metal Ions and Human Diseases.



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