Definition of Thalassemia:

Thalassemias are inherited disorders characterized by abnormal production of hemoglobin. They result in low hemoglobin production, and excessive destruction of red blood cells.

Causes, incidence, and risk factors:

Hemoglobin contains two chains, alpha and beta globin. Genetic abnormalities, which cause an imbalance in the production of either chain, may be inherited.

Beta thalassemias are caused by a mutation in the beta globin chain. The mutated genes must be inherited from both parents to acquire the major form of this disease. If one mutated gene is inherited, the person will be a carrier of the disease, but will not have symptoms. This is the minor form of the disease.

In the major form, children are normal at birth, but develop anemia during the first year of life. Growth failure, bone deformities, and enlarged liver and spleen are some of the problems that can occur. Blood transfusions may modify some of the signs of the disease, but iron overload from the transfusions may cause damage to the heart, liver, and endocrine systems.

The mild form of beta thalassemia produces small red blood cells, with no symptoms. Risk factors include a family history of thalassemia and an ethnic background that has shown susceptibility to the disease.

Beta thalassemias occur in people of Mediterranean origin, and to a lesser extent, Chinese, other Asians, and blacks.

Alpha thalassemias occur most commonly in people from southeast Asia and China, and are caused by deletion of a gene or genes from the alpha globin chain. The most severe form of alpha thalassemia causes stillbirth (death of a fetus before delivery).