Thalassemia is a blood disorder passed down through families (inherited) in which the body makes an abnormal form of hemoglobin, the protein in red blood cells that carries oxygen. The disorder results in excessive destruction of red blood cells, which leads to anemia. Thalassemia, a genetic disease, can be mild or severe. Some carriers of the gene have no symptoms.
Thalassemia is a group of inherited disorders that affects the amount and type of hemoglobin a person produces. Hemoglobin (Hb or Hgb) is found in all red blood cells. A hemoglobin molecule is made up of heme, an iron-containing complex, and globin, protein chains that surround the heme complex. The types of protein chains found in the hemoglobin molecule affect its structure and function. Different types of hemoglobin are classified according to the type of protein chains they contain. Normal hemoglobin types include:
- Hemoglobin A – makes up about 95-98% of the Hb found in adults; Hb A contains two alpha (α) protein chains and two beta (ß) protein chains.
- Hb A2 – makes up about 2-3.5% of Hb found in adults; has two alpha (α) and two delta (δ) protein chains.
- Hb F – makes up to 2% of Hb found in adults; has two alpha (α) and two gamma (γ) protein chains. This is the primary hemoglobin produced by the fetus during gestation. Its production usually falls to a low level within a year after birth.
Mediterranean anemia; Cooley’s anemia; Beta thalassemia; Alpha thalassemia.
Types of Thalassemia
There are two main types: alpha and beta. Beta thalassemia is the most common.
This type occurs when one or more of the four alpha-globin genes that make hemoglobin are missing or damaged.
- If one gene is missing or damaged: You will have no symptoms and will not need treatment. But you are a silent carrier. This means you don’t have the disease but can pass the defective gene to your child.
- If two genes are missing or damaged: You will have very mild anemia that will not need treatment. This is called alpha thalassemia minor or alpha thalassemia trait.
- If three genes are missing: You will have mild to moderately severe anemia. This is sometimes called hemoglobin H disease. If it is severe, you may need blood transfusions.
- If all four genes are missing: This is called alpha thalassemia major. The fetus will be stillborn, or the child will die soon after birth.
You need both alpha- and beta-globin to make hemoglobin. Beta thalassemia occurs when one or both of the two genes that make beta-globin don’t work or only partly work as they should.
- If you have one damaged gene, you may have mild anemia and probably won’t need treatment. This is called beta thalassemia minor or beta thalassemia trait. It happens when you get a normal gene from one parent and a thalassemia gene from the other.
- When both genes are damaged, it means you got a thalassemia gene from each parent. You may have moderate or severe anemia.
- If you have moderate anemia (beta thalassemia intermedia), you may need blood transfusions.
- People with severe anemia (called beta thalassemia major or Cooley’s anemia) need blood transfusions throughout life. Symptoms of anemia usually begin within a few months after birth.
Thalassemia is caused by mutations in the DNA of cells that make hemoglobin — the substance in your red blood cells that carries oxygen throughout your body. The mutations associated with thalassemia are passed from parents to children.
The mutations that cause thalassemia disrupt the normal production of hemoglobin and cause low hemoglobin levels and a high rate of red blood cell destruction, causing anemia. When you’re anemic, your blood doesn’t have enough red blood cells to carry oxygen to your tissues — leaving you fatigued.
Risk factors for thalassemia include:
- Asian, Chinese, Mediterranean, or African American ethnicity
- Family history of the disorder