Thalassemia (thal-uh-SEE-me-uh) is an inherited blood disorder that causes your body to have less hemoglobin than normal. Hemoglobin enables red blood cells to carry oxygen. Thalassemia can cause anemia, leaving you fatigued.If you have mild thalassemia, you might not need treatment. But more severe forms might require regular blood transfusions. You can take steps to cope with fatigue, such as choosing a healthy diet and exercising regularly. Symptoms There are several types of thalassemia. The signs and symptoms you have depend on the type and severity of your condition.Thalassemia signs and symptoms can include:FatigueWeaknessPale or yellowish skinFacial bone deformitiesSlow growthAbdominal swelling Dark urine Some babies show signs and symptoms of thalassemia at birth; others develop them during the first two years of life. Some people who have only one affected hemoglobin gene don't have thalassemia symptoms.When to see a doctor Make an appointment with your child's doctor for an evaluation if he or she has any of the signs or symptoms of thalassemia. Request an Appointment at Mayo Clinic Causes Thalassemia is caused by mutations in the DNA of cells that make hemoglobin — the substance in red blood cells that carries oxygen throughout your body. The mutations associated with thalassemia are passed from parents to children. Hemoglobin molecules are made of chains called alpha and beta chains that can be affected by mutations. In thalassemia, the production of either the alpha or beta chains are reduced, resulting in either alpha-thalassemia or beta-thalassemia.In alpha-thalassemia, the severity of thalassemia you have depends on the number of gene mutations you inherit from your parents. The more mutated genes, the more severe your thalassemia.In beta-thalassemia, the severity of thalassemia you have depends on which part of the hemoglobin molecule is affected.