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Beta Thalassemia

Thalassemia is an inherited disorder that affects the production of normal hemoglobin, a type of protein in red blood cells that carries oxygen to the tissues of the body.

Thalassemia includes a number of different forms of anemia. The severity and type of anemia depends upon the number of genes that are affected.

Causes

Beta thalassemia is caused by mutations in the beta chain of the hemoglobin molecule. There is one beta chain gene on each #11 chromosome, for a total of two. How these genes are altered determines the specific type of beta thalassemia in a child.

There are hundreds of different mutations. Clinically, there are 3 categories of beta thalassemia:

  • Beta thalassemia major (Cooley’s anemia)—both beta chain genes have deletions, causing the most severe type of beta thalassemia.
  • Thalassemia major patients need frequent blood transfusions (more than 8 per year) and may not live a normal life span unless they are adequately treated.
  • They will present during the first 1 to 2 years of life. They can be pale, fussy, have a poor appetite and poor growth.
  • Without treatment, the spleen, liver and heart become enlarged, and bones can become thin and brittle. Treatment with blood transfusions can lead to the build up of iron in the heart and other organs, resulting in heart failure for some patients in their teens or early twenties. Fortunately, there are now medicines that can treat the iron overload and if taken as prescribed, many of these patients are living long lives.
  • Beta thalassemia intermedia—both beta chains have deletions or mutations. However, the degree of anemia is not as severe.
  • Patients with this form of thalassemia may only need occasional blood transfusions.
  • They do need close monitoring by a hematologist as they can develop other problems as they get older.
  • A combination of beta thalassemia trait with Hemoglobin E (common in Southeast Asians) is a clinically significant form of thalassemia intermedia.
  • A combination of beta thalassemia trait with Hemoglobin S/Sickle cell trait is considered a form of sickle cell disease
  • Thalassemia minor or thalassemia trait—one beta gene has a deletion, resulting in mild anemia.

Persons with thalassemia minor have a 50/50 chance to pass the gene to their offspring, who would also have thalassemia minor. Many people are given iron replacement under the mistaken belief that their anemia is the iron-deficient type. Since too much iron can be harmful, it is important to consult a hematologist regarding any treatment.

Thalassemia major and intermedia are inherited in an autosomal recessive pattern, which means that two copies of the gene are necessary to produce the condition, one inherited from each of two carrier parents who have thalassemia minor. There is a 1 in 4, or 25 percent chance with each pregnancy that 2 parents with thalassemia trait will have a child with either thalassemia major or thalassemia intermedia (depends on the combination and severity of the mutations).

Diagnosis

Beta thalassemia is most often found in persons who are of Mediterranean (Greek or Italian), Middle or Far eastern (Asian) ancestry. Each child of two carrier parents is at 25 percent risk for the disease. Carrier status can be determined by the following:

  • Complete blood count (CBC)—a measurement of size, number and maturity of different blood cells in a specific volume of blood
  • Hemoglobin electrophoresis with A2 quantitation—a lab procedure that differentiates the types of hemoglobin present

All of these studies can be performed from a single blood sample. Prenatal diagnosis is determined from chorionic villus sampling (CVS) or amniocentesis.

Treatment

Specific treatment for beta thalassemia major or Cooley’s anemia is determined by your child’s physician based on the following:

  • Your child’s age, overall health and medical history
  • Degree of anemia
  • Your child’s tolerance for specific medications, procedures or therapies
  • Expectations for the course of the disease
  • Your opinion or preference

Treatment for beta thalassemia major or intermedia may include:

  • Regular blood transfusions
  • Medications (to decrease amount of iron in the body, called chelation therapy)
  • Surgical removal of the spleen (if necessary)
  • Daily doses of folic acid
  • Possible surgical removal of the gallbladder
  • No iron supplements
  • Bone marrow transplantation (BMT)

There is no specific treatment need for beta thalassemia trait (minor).