If one gene is inherited, the person will be a carrier of the disease but will not have symptoms. Alpha thalassemias occurs in people from southeast Asia and China, and are caused by deletion of a gene or genes from the globin chain. The most severe form of alpha thalassemia causes a stillborn fetus as a result of hydrops fetalis. Beta thalassemia occurs in people of Mediterranean origin, and to a lesser extent, Chinese, other Asians, and blacks. It is caused by a mutation in the globin chain.
Affected 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 disease manifestation, but iron overload from the transfusions can cause damage to the heart, liver, and endocrine systems. A milder form of the disease, thalassemia minor, produces iron-deficient appearing blood cells, with no symptoms. Risk factors include a family history of thalassemia and an ethnic background susceptible to the disease. The incidence varies widely throughout the world.