23rd May 2023

Overview of thalassaemia

Haemoglobin consists of four polypeptide subunits that contain two alpha chains and two beta chains. Thalassaemias are inherited autosomal recessive genetic disorders that cause reduced synthesis of alpha or beta chains in haemoglobin. This impairs formation of red blood cells, reducing their oxygen-carrying capacity, resulting in microcytic hypochromic anaemia. The defects are caused by genetic point mutations or deletions of key gene fragments. There are two main groups of thalassaemia based on the polypeptide chain that is affected: alpha and beta thalassaemia.

The haemoglobin alpha chain is coded by 4 alleles, leading to a range of severity of alpha thalassaemia, depending on the number of alleles affected. The beta chain is coded by 2 alleles, resulting in only two possible variants of beta thalassaemia.

Alpha thalassaemia predominantly affects those of Asian or African descent, while beta thalassaemia is prevalent in the Mediterranean and Southeast Asian population.

Patients present with a range of phenotypes depending on their inherited thalassaemia trait. These include symptoms of anaemia i.e. fatigue and pallor, slow growth rates in children, jaundice, hepatosplenomegaly, or death in-utero.

Treatment is mainly supportive and includes blood transfusion, oral iron chelating agents to prevent overload, and patient education.