Beta Thalassemia (Cooley's Anemia)
Thalassemia is an inherited disorder that affects the production of normal hemoglobin (a type of iron-rich protein in red blood cells that carries oxygen to the tissues of the body). Thalassemia includes a number of different forms of anemia, which are classified as either alpha thalassemias or beta thalassemias. The severity and type of anemia depends on the number of genes that are affected.
Beta thalassemia is caused by abnormal or missing genes that affect the beta chain of the hemoglobin molecule. There is one beta chain gene on each #11 chromosome, and a total of two #11 chromosomes per person, one inherited from each parent. How these genes are altered determines the specific type of beta thalassemia in a person:
- Beta thalassemia major (Cooley’s anemia). Both #11 chromosomes that an affected person has inherited are abnormal. Both of the chromosomes have abnormal genes that do not direct the body to make normal beta chains or normal amounts of beta chains. Inheriting two abnormal genes causes the most severe type of beta thalassemia. Thalassemia major patients need frequent blood transfusions and may not survive a normal lifespan. During the first one to two years of life, they can be pale, fussy, have a poor appetite, and have many infections. Other signs or symptoms may include growth retardation, abdominal swelling, and jaundice. Without treatment, the spleen, liver, and heart become enlarged, and bones can become thin, brittle, and deformed. A major problem is the buildup of iron from blood transfusions in the heart and other organs, resulting in heart failure for some patients in their teens or early 20s.
- Beta thalassemia minor or thalassemia trait. Only one gene has an abnormality, resulting in less severe anemia. Thalassemia minor is further divided into categories, depending on the patient's presentation:
- Thalassemia minima. A person has few or no symptoms.
- Thalassemia intermedia. A person has moderate to severe anemia.
People with thalassemia minor have a 50/50 chance to pass the gene to their offspring, who would also have thalassemia minor, assuming that the other parent is not affected. 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 demonstrate conclusively that a patient has iron deficiency before beginning treatment. If there is any question as to whether a patient has thalassemia, it is wise to consult a hematologist before beginning any treatment. Thalassemia major is inherited by an autosomal recessive gene, 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.
Beta thalassemia is most often found in people who are of Mediterranean ancestry (Greek or Italian), African, or Asian origin. Each child of two carrier parents is at 25 percent risk for the disease. The diagnosis is typically made at 6 to 12 years of age.
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 hemoglobin F and 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 CVS (chorionic villus sampling) or amniocentesis.
Specific treatment for beta thalassemia major or Cooley's anemia will be determined by your doctor based on:
- Your age, overall health, and medical history
- Extent of the disease
- Your tolerance for specific medications, procedures, or therapies
- Expectations for the course of the disease
- Your opinion or preference
Treatment may include:
- Regular blood transfusions
- Medications (to decrease amount of iron in the body, called iron chelation therapy)
- Splenectomy (surgical removal of the spleen, if necessary)
- Daily doses of folic acid
- Possible surgical removal of the gallbladder
- Regular checks of heart and liver function
- Genetic tests
- No iron supplements
- Bone marrow transplantation has been used; however, the numbers done are limited by the challenge of finding a good donor match and the risks associated with it.
Click here to view the
Online Resources of Hematology `amp; Blood Disorders