Thalassemia is caused by mutations in the DNA of haemoglobin cells passed down from parents to their children. Haemoglobin comprises two types of DNA chains – Alpha and Beta. The condition of thalassemia disease arises when one or both of these chains are affected by mutations.

In Alpha-thalassemia, there are four types of DNA chains, and the severity of the condition depends on the number of mutated chains present. To develop the condition, a person must inherit at least two mutated chains from both parents. If they inherit only one mutated chain, they become disease carriers without displaying any symptoms. The mutations caused by the condition can result in stillbirth or the need for blood transfusion from birth. In contrast, Beta-thalassemia involves only two chains, and the severity of the disease is dependent on the damage caused to the haemoglobin molecules due to the DNA mutation.

Mild symptoms are observed in individuals with a single-chain mutation, while a mutation in both chains leads to more severe symptoms. The onset of symptoms in Beta-thalassemia is slower, with signs usually appearing within two years of birth.