Thalassemias are a group of inherited disorders resulting from an imbalance in the production of one of the four chains of amino acids that make up hemoglobin.
Thalassemias are categorized according to the amino acid chain affected. The two main types are alpha-thalassemia (the alpha chain is affected) and beta-thalassemia (the beta chain is affected). Alpha-thalassemia is most common in blacks (25 percent carry at least one gene), and beta-thalassemia in people from the Mediterranean area and Southeast Asia.
All thalassemias have similar symptoms, but they vary in severity. Most people have a mild anemia. In more severe forms such as beta-thalassemia major, jaundice, skin ulcers, gallstones, and an enlarged spleen (sometimes huge) may develop. Overactive bone marrow may cause some bones, especially those in the head and face, to thicken and enlarge. The long bones may weaken and fracture easily. Children who have thalassemia may grow more slowly and reach puberty later than they normally would. Because iron absorption may be increased and frequent blood transfusions (providing more iron) are needed, excessive iron may accumulate and be deposited in the heart muscle, eventually causing heart failure.
Thalassemias are more difficult to diagnose than other hemoglobin disorders. Testing a drop of blood by electrophoresis is helpful but may be inconclusive, especially for alpha-thalassemia.
Most people who have a thalassemia don't need treatment, but people who have severe forms may need a bone marrow transplantation. Gene therapy is under study.