Thalassaemia

A group of inherited blood disorders in which there is a fault in the production of haemoglobin. Many of the red blood cells become fragile and haemolyse (break up), leading to anaemia (see anaemia, haemolytic). Thalassaemia is prevalent in the Mediterranean, the Middle East, and Southeast Asia, and in families originating from these areas. Normal adult haemoglobin contains 2 pairs of globins (protein chains): alpha and beta. In thalassaemia, a recessive defective gene results in reduced synthesis of 1 of the chains. Usually beta-chain production is disturbed (beta-thalassaemia). Beta-thalassaemia minor (thalassaemia trait), which is never severe, is caused by 1 defective gene. The presence of 2 defective genes causes beta-thalassaemia major (Cooley’s anaemia). The much rarer disorder alpha-thalassaemia varies in severity; alpha-thalassaemia major usually results in fetal death. Symptoms of beta-thalassaemia major appear 3–6 months after birth. If untreated, bone marrow cavities expand, leading to a characteristic enlargement of the skull and facial bones. Beta-thalassaemia major is diagnosed from microscopic examination of the blood, and from other blood tests. Treatment is with blood transfusions and, sometimes, splenectomy. However, successive blood transfusions cause a buildup of iron in the body (see haemosiderosis). Chelating agents are given by continuous infusion to help the body excrete the excess iron. A bone marrow transplant offers a cure for the disease. Genetic counselling is advised for parents or other close relatives of a child with thalassaemia, and also for any person with thalassaemia trait.