Thalassaemias are a group of genetic diseases caused by the production of abnormal haemoglobin, the red coloured protein present in red blood cells that transports oxygen in the body. Haemoglobin comprises two beta (b)-globin and two alpha (a)-globin chains, their production being governed by 2b and 4a genes respectively. In b-thalassaemia, the production of b-chain is abnormal while in a-thal it is the a-chain. When only one beta-globin gene is affected (thal minor or trait or carrier or heterozygous state), it results in mild anaemia not requiring treatment but the involvement of both genes results in severe disease (thalassaemia major or intermedia) requiring regular treatment and follow-up from infancy.
Thalassaemia minor usually is asymptomatic and is typically identified during routine blood examination as mild microcytic anaemia. Individuals generally have no unusual physical findings. A complete blood count (including red cell indices), peripheral smear examination and estimation of Hb A2 & Hb F by HPLC are usually sufficient to diagnose the condition. The normal Hb A2 level in an adult is less than 3.5% and it is elevated (>4%) in b-thalassaemia trait. Even though b-thalassaemia trait is a clinically benign disorder, its importance lies in the fact that if both parents are carriers (i.e. carry one abnormal b-gene), an offspring may co-inherit a b-thalassaemia gene from both the parents making it homozygous resulting in a medically significant thalassaemia (b-thalassaemia major). There are, however, very rare instances where a thal carrier may have normal Hb A2 level and such cases can be detected only by DNA analysis (so called Silent or near silent b-thalassaemia trait).
The goal of long-term hypertransfusional support in a thalassaemic patient is to maintain the patients Hb at 9-10 g/dL, thus improving the patient’s sense of well-being while simultaneously suppressing enhanced erythropoiesis.