What is thalassemia?

Thalassemia is an inherited blood disorder that causes the body to produce less hemoglobin, the protein in red blood cells that helps them carry oxygen from the lungs to all parts of the body. Hemoglobin is made up of four parts: two alpha proteins and two beta proteins. Thalassemia affects one or more of the genes that produce these proteins.

The severity of the disease depends on the type of thalassemia. Children with thalassemia major require ongoing treatment and blood transfusions throughout their lives. In addition, they need ongoing chelation therapy to remove the excess iron that builds up in the blood from these transfusions. Milder forms of thalassemia, including thalassemia intermedia and thalassemia minor, require less aggressive or no treatment at all.

Everyone has four alpha genes and two beta genes that together control the production of hemoglobin. There are three major types of thalassemia, classified based on the severity of symptoms and the genetic defect causing the disease.

What are the types of thalassemia?

Thalassemia minor and silent carriers

Children with thalassemia minor or trait have two alpha genes or one beta gene missing or damaged, while those that are “silent carriers” have one missing or damaged alpha gene. These children do not experience symptoms (except mild anemia in some cases of thalassemia minor), and they do not require treatment.

Thalassemia intermedia

In children with beta thalassemia intermedia, one or both beta genes are not working properly. They have mild to severe anemia andcan be diagnosed early in childhood or later in life. They may need blood transfusions during pregnancy or when very sick.

Thalassemia major

Children with thalassemia major need ongoing medical care, including blood transfusions to alleviate severe anemia and chelation therapy to remove excess iron from the blood.There are two subtypes of thalassemia major:

Alpha thalassemia major

  • most serious and most rare form of the subtypes of thalassemia
  • all four alpha genes are missing
  • if untreated, leads to miscarriage or death of the baby shortly after birth
  • may be treated with blood transfusions in the womb if discovered early enough in the pregnancy
  • babies who survive require lifelong blood transfusions or stem cell transplant and extensive medical care

Beta thalassemia major (also called Cooley’s anemia, after the discoverer)

    • neither beta gene is not working properly
    • symptoms, which begin during the first year of life, include severe anemia
    • monthly blood transfusions needed
    • chelation therapy also is needed to remove excess iron that builds up in the body due to frequent blood transfusions

    Other types of thalassemia

    • Hemoglobin E beta-thalassemia: This form of thalassemia is more common in children of Southeast Asian descent. It results from two separate genetic defects:
    • Hemoglobin H disease alpha-thalassemia: This form of thalassemia is most common in Southern China and Southeast Asia. In Hemoglobin H disease:

    The defective genes that cause thalassemia are relatively common, especially in people of South Asian, African and Mediterranean descent. However, thalassemia occurs in many populations around the world.

    About 300 million people around the world have the “thalassemia trait,” which puts them at risk of having children with some form of thalassemia. More than 1 million people have thalassemia intermedia, while more than 100,000 people have thalassemia major. In the United States, there are only about 1,000 people with thalassemia major.

    Hemoglobin H disease and hemoglobin E/beta thalassemia are extremely common in Southern China, and South and Southeast Asia.

    How we care for thalassemia

    At the Dana-Farber/Boston Children’s Cancer and Blood Disorders Thalassemia Program, our experts provide comprehensive care for children and adults with all forms of thalassemia. For many appointments and certain procedures, your child also can receive care at one of our satellite offices. Treatment for thalassemia depends on the subtype of the disorder, but may include:

    • blood transfusions for anemia, based on severity
    • regular and comprehensive monitoring for complications of thalassemia and of treatments
    • iron chelation therapy, to remove excess iron from the body
    • for certain cases, stem cell transplantation to replace the blood-forming stem cells with the defective hemoglobin gene(s)

    What is the latest thalassemia research?

    We are involved in a number of research initiatives aimed at improving thalassemia care including:

    • investigating the effectiveness of new oral iron chelators, drugs that remove excess iron from the body
    • improving existing chelation therapies and investigating new ones
    • using stem cell transplants to cure patients with transfusion dependent thalassemia
    • developing new ways to assess iron levels in the body
    • understanding how to use gene therapy to force red blood cells to make a form of hemoglobin called fetal hemoglobin, which our cells make until birth and which is not affected by the genetic defects that cause thalassemia

    Clinical Trials

    For many children with rare or hard-to-treat conditions, clinical trials provide new options. Search our open clinical trials.