Types of Thalassemia
The type of thalassemia depends on the number of gene mutations one inherits from their parents and which part of the hemoglobin molecule is affected by the mutations. The more mutated genes, the more severe the thalassemia. Hemoglobin molecules are made of alpha and beta parts that can be affected by mutations.
Four genes are involved in making the alpha hemoglobin chain. Every person receives two from each of their parents. If one inherits:
- mutated gene, the person will have no signs or symptoms of thalassemia. But the person will be a carrier of the disease and can pass it on to their children.
- mutated genes, thalassemia signs and symptoms will be mild. This condition may be called alpha-thalassemia trait.
- mutated genes, signs and symptoms will be moderate to severe.
- mutated genes. This type is rare. Affected fetuses have severe anemia and usually are stillborn. Babies born with this condition often die shortly after birth or require lifelong transfusion therapy. In rare cases, a child born with this condition may be treated with transfusions and a stem cell transplant, which is also called a bone marrow transplant.
Two genes are involved in making the beta hemoglobin chain. One gets one from each of
their parents. If one inherits:
- mutated gene, the person will have mild signs and symptoms. This condition is called thalassemia minor or beta-thalassemia.
- mutated genes, the signs and symptoms will be moderate to severe. This condition is called thalassemia major, or Cooley anemia. Babies born with two defective beta hemoglobin genes usually are healthy at birth but develop signs and symptoms within the first two years of life. A milder form, called thalassemia intermedia, also may occur with two mutated genes.