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Disease Profile


Prevalence estimates on Rare Medical Network websites are calculated based on data available from numerous sources, including US and European government statistics, the NIH, Orphanet, and published epidemiologic studies. Rare disease population data is recognized to be highly variable, and based on a wide variety of source data and methodologies, so the prevalence data on this site should be assumed to be estimated and cannot be considered to be absolutely correct.


US Estimated

Europe Estimated

Age of onset





Autosomal dominant A pathogenic variant in only one gene copy in each cell is sufficient to cause an autosomal dominant disease.


Autosomal recessive Pathogenic variants in both copies of each gene of the chromosome are needed to cause an autosomal recessive disease and observe the mutant phenotype.


dominant X-linked dominant inheritance, sometimes referred to as X-linked dominance, is a mode of genetic inheritance by which a dominant gene is carried on the X chromosome.


recessive Pathogenic variants in both copies of a gene on the X chromosome cause an X-linked recessive disorder.


Mitochondrial or multigenic Mitochondrial genetic disorders can be caused by changes (mutations) in either the mitochondrial DNA or nuclear DNA that lead to dysfunction of the mitochondria and inadequate production of energy.


Multigenic or multifactor Inheritance involving many factors, of which at least one is genetic but none is of overwhelming importance, as in the causation of a disease by multiple genetic and environmental factors.


Not applicable



Blood Diseases


Thalassemia is an inherited blood disorder that reduces the production of functional hemoglobin (the protein in red blood cells that carries oxygen). This causes a shortage of red blood cells and low levels of oxygen in the bloodstream, leading to a variety of health problems.[1] There are two main types of thalassemia, alpha thalassemia and beta thalassemia. Signs and symptoms vary but may include mild to severe anemia, paleness, fatigue, yellow discoloration of skin (jaundice), and bone problems.[2] Beta thalassemia is caused by changes (mutations) in the HBB gene while alpha thalassemia is caused by mutations in the HBA1 and/or HBA2 genes. Both are inherited in an autosomal recessive manner.[3][4] Treatment depends on the type and severity of the condition but may include blood transfusions and/or folic acid supplements.[5][2]


The signs and symptoms vary depending on the severity of the thalassemia. For example, people affected by milder forms of thalassemia can develop mild anemia or may have no signs or symptoms of the condition at all. Intermediate forms of thalassemia can cause mild to moderate anemia and may be associated with other health problems such as slowed growth, delayed puberty, bone problems and/or an enlarged spleen. In addition to the signs and symptoms seen in intermediate thalassemia, people with severe forms of thalassemia may also experience severe anemia, poor appetite, paleness, dark urine, yellow discoloration of skin (jaundice), and enlarged liver or heart.[2][1][5]

For more information on the signs and symptoms by type of thalassemia, please click here.


There are two main types of thalassemia, alpha thalassemia and beta thalassemia, which each affect a different part of hemoglobin (the protein in red blood cells that carries oxygen). Hemoglobin is made up of two different components (subunits): beta globin and alpha globin. The HBB gene provides instructions for making beta globin, while the HBA1 and HBA2 genes provide instructions for making alpha globin. Each person has two copies of each of these genes, one inherited from the mother and one from the father. Changes (mutations) in the HBB gene lead to reduced levels of beta globin and cause beta thalassemia. Loss (deletion) of some or all of the HBA1 and/or HBA2 genes results in a shortage of alpha globin, leading to alpha thalassemia.[3][4]


Yes, genetic testing is available for HBB, HBA1 and HBA2, the genes known to cause thalassemia.[3][4] Carrier testing for at-risk relatives and prenatal testing are possible if the disease-causing mutations in the family are known.

The Genetic Testing Registry (GTR) is a centralized online resource for information about genetic tests. It has additional information on genetic testing for alpha thalassemia and beta thalassemia. The intended audience for the GTR is health care providers and researchers. Patients and consumers with specific questions about a genetic test should contact a health care provider or a genetics professional.

Testing Resources

  • The Genetic Testing Registry (GTR) provides information about the genetic tests for this condition. The intended audience for the GTR is health care providers and researchers. Patients and consumers with specific questions about a genetic test should contact a health care provider or a genetics professional.


    The best treatment options depend on the severity of thalassemia. People affected by a mild form often need little to no treatment, while people with intermediate to severe thalassemias may require frequent blood transfusions, iron chelation therapy (treatments to remove excess iron from the body), and/or folic acid supplementation.[2][1]

    For more information on the treatment of thalassemia, please click here.


    Support and advocacy groups can help you connect with other patients and families, and they can provide valuable services. Many develop patient-centered information and are the driving force behind research for better treatments and possible cures. They can direct you to research, resources, and services. Many organizations also have experts who serve as medical advisors or provide lists of doctors/clinics. Visit the group’s website or contact them to learn about the services they offer. Inclusion on this list is not an endorsement by GARD.

    Organizations Supporting this Disease

      Learn more

      These resources provide more information about this condition or associated symptoms. The in-depth resources contain medical and scientific language that may be hard to understand. You may want to review these resources with a medical professional.

      Where to Start

      • You can obtain information on this topic from the Centers for Disease Control and Prevention (CDC). The CDC is recognized as the lead federal agency for developing and applying disease prevention and control, environmental health, and health promotion and education activities designed to improve the health of the people of the United States.
      • The Mayo Clinic Web site provides further information on Thalassemia.
      • MedlinePlus was designed by the National Library of Medicine to help you research your health questions, and it provides more information about this topic.
      • The Merck Manual provides information on this condition for patients and caregivers.
      • The National Heart, Lung, and Blood Institute (NHLBI) has information on this topic. NHLBI is part of the National Institutes of Health and supports research, training, and education for the prevention and treatment of heart, lung, and blood diseases.
      • The National Human Genome Research Institute's (NHGRI) website has an information page on this topic. NHGRI is part of the National Institutes of Health and supports research on the structure and function of the human genome and its role in health and disease.

        In-Depth Information

        • The Merck Manual for health care professionals provides information on Thalassemia.
        • The Monarch Initiative brings together data about this condition from humans and other species to help physicians and biomedical researchers. Monarch’s tools are designed to make it easier to compare the signs and symptoms (phenotypes) of different diseases and discover common features. This initiative is a collaboration between several academic institutions across the world and is funded by the National Institutes of Health. Visit the website to explore the biology of this condition.
        • PubMed is a searchable database of medical literature and lists journal articles that discuss Thalassemia. Click on the link to view a sample search on this topic.


          1. Thalassemia. MedlinePlus. February 2014; https://www.nlm.nih.gov/medlineplus/ency/article/000587.htm.
          2. Explore Thalassemias. National Heart, Lung, and Blood Institute. July 2012; https://www.nhlbi.nih.gov/health/health-topics/topics/thalassemia.
          3. Beta thalassemia. Genetics Home Reference. July 2009; https://ghr.nlm.nih.gov/condition/beta-thalassemia. Accessed 12/5/2010.
          4. Alpha thalassemia. Genetics Home Reference. August 2009; https://ghr.nlm.nih.gov/condition/alpha-thalassemia. Accessed 1/23/2012.
          5. Hassan M Yaish, MD. Pediatric Thalassemia. Medscape Reference. April 2013; https://emedicine.medscape.com/article/958850-overview.

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