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Difference Between Alpha Thalassemia and Beta Thalassemia
Thalassemia is a group of inherited blood disorders that affect the production of hemoglobin, the protein that carries oxygen in the blood. It is caused by mutations in the genes that control the production of hemoglobin. There are two main types of thalassemia: alpha thalassemia and beta thalassemia. Although they share similar symptoms, they are caused by different genetic mutations and have different degrees of severity.
What is Alpha Thalassemia?
Alpha thalassemia is the condition where there is a reduced formation of alpha polypeptide chains because of an absence of alpha genes. There are two forms of alpha thalassemia depending on what genes are missing. Alpha + is when only one gene is missing from chromosome 16, while alpha 0 is when both genes are lacking from the same chromosome.
Symptoms − In some cases, there may be no symptoms and a person can be a carrier. This is often the situation where it is the alpha + form, and only one allele is affected. In other cases, where two alleles are missing, there are some symptoms such as smaller than normal red blood cells (microcytic anemia). In this case, there will be symptoms but they will not be too severe. If three of four alleles are missing then symptoms can be very bad and may include paleness, fatigue, swollen spleen, and jaundice. Such people may develop hemolytic anemia. If all four genes are affected a fetus will have Bart’s hydrops fetalis, and will not survive.
Diagnosis − The diagnosis is based on the examination of a smear of blood that shows very small red blood cells. Fetal hemoglobin and hemoglobin A2 is usually normal in alpha thalassemia. Genetic testing can show deletions of alleles and electrophoresis of hemoglobin can show the condition as well. Fetal tissue can also be removed to test for the condition.
Causes and Risk Factors − The condition is inherited and is due to a genetic mutation of the alpha genes that are responsible for making alpha polypeptide chains. This condition is more common in people who are of Southeast Asian, African descent, or are from the Mediterranean regions of Cyprus and Greece.
Prevention and Treatment − Genetic screening and counseling can help detect if there are genetic anomalies. Measuring hemoglobin levels in a couple may also help to show if they are carrying an alpha gene mutation. Sometimes a stem cell transplant while the fetus is in utero can cure them, or else the patient will need lifelong transfusions and potentially chelation therapy to remove excess iron from the blood. If the spleen becomes enlarged this may need to be surgically removed.
What is Beta Thalassemia?
Beta thalassemia is where there is a reduced formation of beta polypeptide chains because of mutations in the beta globin genes that occur on chromosome 11. There are two types of beta thalassemia; one type is when only partial loss of function occurs. This is beta + thalassemia. The other type is the complete loss of function, which is beta 0 thalassemia.
Symptoms − The symptoms vary depending on the extent of the damage to the genes. Individuals with few problems with beta globulin production are often silent carriers who show no symptoms. Some people are intermediate and may show some symptoms. Major beta thalassemia (Cooley’s anemia), occurs when there are severe symptoms such as problems with the bone marrow, and severe anemia. Such patients can appear very pale; have jaundice, leg ulcers, enlarged spleens, and even gallstone formation.
Diagnosis − Beta thalassemia is diagnosed by looking for hemolytic anemia by examining a red blood cell smear under the microscope. Testing of hemoglobin can be done and with severe beta thalassemia the hemoglobin would be low, less than 6 g/dL. There would be higher than average fetal hemoglobin and hemoglobin A2 in certain types of beta thalassemia.
Causes and Risk Factors − This is inherited and is due to some type of genetic change (mutation) that has occurred in the beta globin genes. Beta thalassemia is more commonly found in people who are of Southeast Asian, African or Mediterranean descent.
Prevention and Treatment − Genetic screening and hemoglobin testing can indicate if a person is carrying the mutation. Treatment may require blood transfusions, and chelation therapy to remove excess iron due to the transfusions, and in some cases, spleen removal is needed.
Differences: Alpha and Beta Thalassemia
Alpha thalassemia is caused by mutations in the genes that control the production of alpha globin, one of the two types of protein chains that make up hemoglobin. There are four genes that control the production of alpha globin, and each person inherits two copies of these genes, one from each parent. If one or more of these genes is mutated, it can lead to a decrease in the production of alpha globin, resulting in a type of anemia known as alpha thalassemia.
There are four types of alpha thalassemia, depending on the number of alpha globin genes that are mutated. The mildest form is alpha thalassemia silent carrier, which occurs when one alpha globin gene is mutated. People with this form of thalassemia do not usually experience any symptoms and are usually unaware that they carry the gene mutation.
Alpha thalassemia trait occurs when two alpha globin genes are mutated, leading to mild anemia. Hemoglobin H disease occurs when three alpha globin genes are mutated, leading to moderate to severe anemia. People with this form of thalassemia may experience symptoms such as fatigue, weakness, pale skin, and enlargement of the spleen. The most severe form of alpha thalassemia is alpha thalassemia major, which occurs when all four alpha globin genes are mutated, leading to severe anemia and fetal hydrops, a life-threatening condition in which fluid builds up in the fetus’s body.
Beta thalassemia, on the other hand, is caused by mutations in the genes that control the production of beta globin, the other type of protein chain that makes up hemoglobin. There are two genes that control the production of beta globin, and each person inherits one copy of these genes from each parent. If one or both of these genes are mutated, it can lead to a decrease in the production of beta globin, resulting in a type of anemia known as beta thalassemia.
There are two main types of beta thalassemia: "beta thalassemia minor" and "beta thalassemia major". Beta thalassemia minor occurs when one beta globin gene is mutated, leading to mild anemia. People with this form of thalassemia may experience symptoms such as fatigue, weakness, and pale skin. Beta thalassemia major, also known as Cooley’s anemia, occurs when both beta globin genes are mutated, leading to severe anemia and other complications. People with this form of thalassemia may require regular blood transfusions to survive.
The following table highlights the major differences between Alpha Thalassemia and Beta Thalassemia −
Characteristics |
Alpha Thalassemia |
Beta Thalassemia |
|---|---|---|
Definition |
Alpha thalassemia is where there is a reduced formation of the alpha polypeptides. |
Beta thalassemia is where there is a reduced formation of the beta polypeptides. |
Symptoms |
In alpha thalassemia there can be no symptoms or in severe cases hemolytic anemia and an enlarged spleen, paleness, jaundice, and fatigue. |
In beta thalassemia, there can be no symptoms or in severe cases, there can be issues with the bone marrow as well as problems such as severe anemia, jaundice, gallstones, and enlarged spleens. |
Diagnosis |
Alpha thalassemia is diagnosed by the presence of very small red blood cells in a red blood cell smear; genetic testing and electrophoresis of hemoglobin. |
Beta thalassemia is diagnosed by noting hemolytic anemia in a red blood cell smear; hemoglobin testing may indicate higher than average fetal hemoglobin, and hemoglobin A2.or lower than normal overall hemoglobin values. |
Causes |
A mutation of one or more of the alpha genes on chromosome 16, causes alpha thalassemia. |
A mutation of one or more of the beta globin genes on chromosome 11 causes beta thalassemia. |
Conclusion
In summary, alpha thalassemia and beta thalassemia are two types of inherited blood disorders that affect the production of hemoglobin. Alpha thalassemia is caused by mutations in the genes that control the production of alpha globin, while beta thalassemia is caused by mutations in the genes that control the production of beta globin.
Both types of thalassemia can range from mild to severe, depending on the number and type of gene mutations present. Proper diagnosis and treatment are important.
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