Thalassemias are inherited blood disorders that cause the body to make fewer healthy red blood cells and less hemoglobin than normal. Mild or severe anemia can also be present in people with thalassemias.
The two major types of thalassemia are alpha and beta, named after defects in the hemoglobin protein chains. The most severe form of alpha thalassemia is known as alpha thalassemia major or hydrops fetalis. Babies with this disorder usually die before or shortly after birth. Two genes (one from each parent) are needed to make enough beta globin protein chains. Beta thalassemia occurs when one or both genes are altered. The severity of beta thalassemia depends on how badly one or both genes are affected. If both genes are affected, the result is moderate to severe anemia. The severe form of beta thalassemia also is known as thalassemia major or Cooley's anemia.
Thalassemias occur most often among people of Italian, Greek, Middle Eastern, Asian, and African descent. Severe forms usually are diagnosed in early childhood and are lifelong conditions.