Beta thalassemia: inheritance, symptoms, and disease mechanisms

Beta Thallasemia

Beta Thalassemia

Beta thalassemia is the severer of the two main types of thalassemia -- an inherited blood disease resulting from defective production of hemoglobin. About 100,000 people are born worldwide every year with beta thalassemia which occurs most frequently in people of Italian, Greek, Middle Eastern, Southern Asian and African Ancestry. (Learning about...," 2004) People with beta thalassemia usually develop anemia, resulting in inadequate delivery of oxygen to the body's tissues and it proves fatal in most cases, if left untreated. In this paper we shall discuss the disease develops; the types of beta thalassemia, how it is inherited, its symptoms, diagnosis and treatment.

How Beta Thalassemia develops?

Hemoglobin, the protein that transports oxygen in the blood, is made up of four chains of amino acids: two identical alpha chains and two identical beta chains. Thalassemia is the result of an imbalance in the production of beta chains that is caused by a mutation in the genes that direct their production. A mutation to the beta genes decreases the production of beta chains, resulting in beta thalassemia.

Types of Beta Thelassemia

There are two forms of beta thalassemia: thalassemia minor and thalassemia major (which is also called Cooley's anemia after the physician who first discovered the disease).

Thalassemia minor occurs in a person who has only one copy of the beta thalassemia gene (together with one perfectly normal beta-chain gene). It causes only mild anemia and normally no treatment is necessary for the affliction. A person with Thalassemia major (Cooley's anemia) has two genes for beta thalassemia and no normal beta-chain gene causing a severe deficiency in beta chain production. It is a serious disease and proves fatal, if left untreated. ("Beta Thalassemia" Medicine.net, 2004)

How is Beta Thelassemia Inherited?

Each person has two copies of the beta gene, one inherited from each parent. Beta thalassemia results when both copies of the beta gene are abnormal. A person with only one abnormal copy of the beta gene does not develop the disease but is a carrier of beta thalassemia. When two carriers of beta thalassemia have children, each child has a 25% chance of inheriting two abnormal copies of the beta gene and, therefore, developing the disease. Each child has a 50% chance of inheriting one abnormal gene and being a carrier, and a 25% chance of inheriting two normal beta genes. A carrier of beta thelassamia does not develop any symptoms of the disease but can pass on the disease to their children. (Nathan and Nisbet-Brown, 2003)

Diagnosis

Symptoms such as poor growth and enlargement of the liver and spleen are the first signs that a child may have thalassemia. However, for a firm diagnosis, a doctor usually performs several types of blood tests and examines the family medical history of the patient. A blood count is taken that reveals the number of red cells present -- a low count being indicative of anemia. A technique known as hemoglobin electrophoresis is used by doctors to isolate different types of hemoglobin in a patient's blood, and distinguish between normal individuals, carriers, and thalassemia patients. The method is also used to test a child's parents and if it is established that both are carriers; it helps to confirm the diagnosis. ("Beta Thellasemia," Child Health, 2001)

Recently, prenatal diagnosis of thalassemia has become possible through procedures such as amniocentesis and chorionic villus sampling. This enables couples the choice of aborting affected fetuses. It is also now possible to pinpoint the type of thalassemia mutation afflicting a patient, which allows doctors to predict the severity of the patient's disease. (Nathan, 2003)

Treatment

Frequent blood transfusions keep the hemoglobin levels near normal but repeated blood transfusions lead to iron overload that can damage the heart, liver and other organs. Drugs known as iron chelators can help rid the body of excess iron. Bone marrow transplant is another method of treatment but it is possible only for a small minority of patients who have a suitable bone marrow donor. The transplant procedure is risky and can result in death. Scientists are working to develop a gene therapy that may offer a better cure for thalassemia. It could involve the insertion of a normal beta globin gene into the patient's stem cells or the development of drugs that reactivate the patient's genes that produce fetal hemoglobin. (Learning about...," 2004) Till such time Beta Thallasemia is likely to remain a serious and frequently fatal disease for thousands of afflicted people around the world.