Beta thalassemia is an inherited blood disorder characterized by the abnormal production of a blood protein called hemoglobin. This condition is caused by a mutation within the gene that is responsible for the healthy production of hemoglobin. In healthy people, hemoglobin carries oxygen to tissues and cells throughout the body. Patients with beta thalassemia do not have adequate levels of oxygen within the blood, which can cause anemia. There are two main types of beta thalassemia with symptoms that range from mild to severe.
Beta-globin is produced by two genes, one gene from each parent.
The severity of the condition correlates with the amount of normal beta-globin production. Beta Thalassemia Minor The individuals with thalassemia minor have only one copy of the beta thalassemia gene. These individuals are said to be heterozygous for beta thalassemia and will have mild anemia. This situation can vary closely resemble that with mild iron-deficiency anemia. However, people with thalassemia minor have a normal blood iron level.
No treatment is necessary for thalassemia minor. In particular, iron is neither necessary nor advised Beta Thalassemia Major.
The child born with thalassemia major has two genes for beta thalassemia and no normal beta chain gene. The child is homozygous for beta thalassemia. This causes a striking deficiency in beta chain production and in the production of HBA. The clinical picture associated with thalassemia major was first described in 1925 by the American pediatrician Thomas Cooley. Hense, the name Cooley’s anemia in his honor. At birth the baby with thalassemia major seems entirely normal.
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Anemia begins to develop within the first months after birth. It becomes progressively more and more severe.
Chromosome location The gene controlling beta chain production is located on the short (p) arm of chromosome 11 at position 15. 5. More precisely, The HBB gene is located from base pair 5,203,271 to base pair 5,204,876 on chromosome 11. Characteristics of the Disease Beta thalassema major is characterized by severe anemia that can begin months after birth. In the United States and other developed countries, beta thalassemia is identified and treated early and effectively. In untreated, beta thalassemia major can lead to severe tiredness, jaundice, and growth and developmental delay.
The body attempts to compensate by producing more blood cells in the bone marrow. However, this is ineffective without the needed genetic instructions to make enough functioning hemoglobin. Instead, obvious bone expansion and changes occur that cause characteristics facial and other changes in appearance, as well as increased risk of fractures. Severe anemia affects other organs in the body such as the heart, spleen, and liver. This can lead to heart failure and enlargement of the the liver and spleen. When untreated, beta thalassemia major generally results in childhood death, usually due to heart failure.
Fortunately, in developed countries diagnosis is usually made early, often before symptoms have begun. This allows for treatment with blood transfusion therapy, which can prevent most of the complications of the severe anemia caused by beta thalassemia major. A compelet blood count will identify low levels of hemoglobin and other red blood cell abnormalities that are characterized with beta thalassemia. Since thalassemia trait can sometimes be difficult to distinguish from iron deficiency, tests to evaluate iron levels are important.
A hemoglobin electrophoresis is a test that can help identify the types and quantities of hemoglobin made by an individual. This test uses an electric field applied across a slab of gel-like material. Hemoglobins migrate through this gel at various rates and to specific locations, depending on their size, shape, and electrical charge. In addition, isoelectric focusing and high-performance liquid chromatography (HPLC) use similar principles to separate hemoglobins and can be used instead of or in various combination with hemoglobin electrophoresis to determine the types and quantities of hemoglobin present.
Hemoglobin electrophoresis results are usually within the normal range for all types of alpha thalassemia. However, hemoglobin A2 levels and sometimes hemoglobin F levels are elevated when beta thalassemia disease or trait is present. Hemoglobin electrophoresis can also detect structurally abnormal hemoglobins that may be co-inherited with a thalassemia trait to cause thalassemia disease or other types of hemoglobin disease. Sometimes DNA testing is needed in addition to the screening tests. This can be performed to help confirm that diagnosis and establish the exact genetic type of thalassemia.
Treatment or Management of the Condition The most common treatment of all major forms of thalassemia is red blood cell transfusions. These transfusions are necessary to provide the patient with a temporary supply of healthy red blood cells with normal hemoglobin capable of carrying the oxygen that the pateint’s body needs. While thalassemia patients were given infrequent transfusions in the past, clinical research led to a more frequent program of regular blood cell transfusions that greatly improved the patient’s quality of life.
Today, most patients with a major form of thalassemia receive red blood cell transfusions every two to three weeks, amounting to as much as 52 pints of blood a year. Because there is no natural way to the body to eliminate iron, the iron in the transfused blood cells builds up in a condition known as iron overload and becomes toxic to tissues and organs, particularly the liver and heart. To help remove excess iron, patients undergo iron chelation therapy, in which a drug introduced into the body which binds with excess iron and removes it through the urine or stool.
In 2005, FDA approved an oral chelator, Exjade. This is a pill which is dissolved in water or juice once a day. Molecular Genetics Beta thalassemia is caused by mutations in the HBB gene. More than 250 mutations in the HBB gene have been caused beta thalssemia. Most of the mutations involve a change in single DNA building block within or near the HBB gene. Other mutations insert or delete a small number of nucleotides in the HBB gene. HBB gene mutations that decrease beta-globin production result in a type of the condition called beta-plus thalssemia.
Mutations that prevent cells from producing any beta-globin result in beta-zero thalssemia. Without proper amounts of beta-globin, sufficient hemoglobin cannot be formed. A lack of hemoglobin disrupts the normal development of red blood cells. A shortage of mature red blood cells prevents these cells from carrying and delivering enough oxygen to satisfy the body’s energy needs. A lack of oxygen in the body’s tissues can lead to poor growth, organ damage, and other health problems associated with beta thalassemia. Genetic Testing
DNA analysis is available to investigate deletions and mutations in the beta-globin producing genes. Family studies can be done to evaluate carrier status and the types of mutations present in family members. DNA testing is not routinely done but can be used to help diagnosis thalassemia and to determine carrier status. Other relevant information Being a carrier of the disease may confer a degree of protection against malaria, as it is quite common among people of Italian and Greek origin, and also in some African and Indian regions.
This probably by making the red blood cells more susceptible to the less lethal species Plasmodium vivax simultaneously making the host’s red blood cell environment unsuitable for the more lethal strain Plasmodium falciparum. This is believed to be a selective advantage for patients with the various thalassemia traits.
Disease Beta Thalassemia With Gene Mutation. (2019, Dec 06). Retrieved from https://paperap.com/paper-on-thalassemia-26/
