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Disease Profile

Sickle beta thalassemia

Prevalence
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.

Unknown

Age of onset

All ages

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ICD-10

D57.2

Inheritance

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

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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

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X-linked
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.

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

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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.

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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.

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Not applicable

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Other names (AKA)

Hemoglobin sickle-beta thalassemia; Hb S beta-thalassemia; Sickle cell beta-thalassemia disease;

Categories

Blood Diseases; Congenital and Genetic Diseases; Endocrine Diseases;

Summary

Sickle beta thalassemia is an inherited condition that affects hemoglobin, the protein in red blood cells that carries oxygen to different parts of the body. It is a type of sickle cell disease. Affected people have a different change (mutation) in each copy of their HBB gene: one that causes red blood cells to form a "sickle" or crescent shape and a second that is associated with beta thalassemia, a blood disorder that reduces the production of hemoglobin. Depending on the beta thalassemia mutation, people may have no normal hemoglobin (called sickle beta zero thalassemia) or a reduced amount of normal hemoglobin (called sickle beta plus thalassemia). The presence of sickle-shaped red blood cells, which often breakdown prematurely and can get stuck in blood vessels, combined with the reduction or absence of mature red blood cells leads to the many signs and symptoms of sickle beta thalassemia. Features, which may include anemia (low levels of red blood cells), repeated infections, and frequent episodes of pain, generally develop in early childhood and vary in severity depending on the amount of normal hemoglobin made. Sickle beta thalassemia is inherited in an autosomal recessive manner. Treatment is supportive and depends on the signs and symptoms present in each person.[1][2][3]

Symptoms

Signs and symptoms of sickle beta thalassemia may include:[3][4]

  • Anemia (low levels of red blood cells)
  • Repeated infections
  • Frequent episodes of pain
  • Pulmonary hypertension
  • Acute chest syndrome (pneumonia-like condition due to entrapment of infection or sickle cells in the lungs)
  • Stroke
  • Enlarged spleen and/or liver
  • Heart murmurs
  • Delayed puberty
  • Slowed growth
  • Jaundice

The symptoms of sickle beta thalassemia vary in severity based on the amount of normal hemoglobin made. Affected people may have no normal hemoglobin (called sickle beta zero thalassemia) or a reduced amount of normal hemoglobin (called sickle beta plus thalassemia). Although these two forms share many of the same features, people with sickle beta zero thalassemia are generally more severely affected than those with sickle beta plus thalassemia. For example, people with sickle beta plus thalassemia generally experience less frequent episodes of pain and are less likely to develop stroke, pulmonary hypertension and acute chest syndrome.[4]

Cause

Sickle beta thalassemia is caused by changes (mutations) in the HBB geneHBB encodes a component of hemoglobin called "beta globin". Different mutations in HBB impact the production of hemoglobin in various ways. One specific mutation leads to an abnormal form of hemoglobin (called hemoglobin S) that causes red blood cells to form a "sickle" or crescent shape. Other mutations reduce the production of beta globin, which leads to low levels of functional hemoglobin and a low number or mature red blood cells (beta thalassemia).[2]

People affected by sickle beta thalassemia have a different mutation in each copy of the HBB gene: one that produces hemoglobin S and a second that is associated with beta thalassemia. Depending on the beta thalassemia mutation, people may have no normal hemoglobin (called sickle beta zero thalassemia) or a reduced amount of normal hemoglobin (called sickle beta plus thalassemia). The presence of sickle-shaped red blood cells, which often breakdown prematurely and can get stuck in blood vessels, combined with the reduction or absence of mature red blood cells leads to the many signs and symptoms of sickle beta thalassemia.[2]

Diagnosis

In the United States, babies affected by sickle beta thalassemia are often diagnosed at birth through newborn screening. In the absence of newborn screening, a diagnosis is usually suspected in infants or young children with signs and symptoms associated with the condition. Specialized laboratory tests that measure the amounts of abnormal hemoglobin in the blood and/or genetic testing to identify changes (mutations) in the HBB gene can be used to confirm a diagnosis.[1]

Carrier testing for at-risk relatives and prenatal testing are possible if both disease-causing mutations in the family are known.[1] 

The Genetic Testing Registry (GTR) is a centralized online resource for information about genetic tests. 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.

Newborn Screening

  • An ACTion (ACT) sheet is available for this condition that describes the short-term actions a health professional should follow when an infant has a positive newborn screening result. ACT sheets were developed by experts in collaboration with the American College of Medical Genetics.
  • An Algorithm flowchart is available for this condition for determining the final diagnosis in an infant with a positive newborn screening result. Algorithms are developed by experts in collaboration with the American College of Medical Genetics.
  • Baby's First Test is the nation's newborn screening education center for families and providers. This site provides information and resources about screening at the local, state, and national levels and serves as the Clearinghouse for newborn screening information.
  • The Newborn Screening Coding and Terminology Guide has information on the standard codes used for newborn screening tests. Using these standards helps compare data across different laboratories. This resource was created by the National Library of Medicine.
  • National Newborn Screening and Global Resource Center (NNSGRC) provides information and resources in the area of newborn screening and genetics to benefit health professionals, the public health community, consumers and government officials.

    Treatment

    Treatment for sickle beta thalassemia is supportive and usually depends on the signs and symptoms present in each person. It is generally recommended that all affected people drink plenty of water; avoid climate extremes, activities that lead to inflammation and extreme fatigue; and stay up-to-date on all immunizations. Because sickle beta thalassemia is associated with a variety of health problems, affected people are usually followed closely by their healthcare provider with regular physical examinations that may include specialized laboratory tests and imaging studies (i.e. chest X-ray, transcranial doppler ultrasound, ECG). Blood transfusions may be prescribed on a regular basis for affected people with a history of or risk factors for stroke and other specific health problems, such as pulmonary hypertension. Hydroxyurea, a drug approved by the U.S. Food and Drug Administration for the treatment of sickle cell disease, can decrease the frequency and severity of pain episodes; reduce the need of blood transfusions; and increase life span.[1][3]

    For more information regarding the treatment of sickle beta thalassemia and other sickle cell diseases, please click here.

    Organizations

    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.
      • Genetics Home Reference (GHR) contains information on Sickle beta thalassemia. This website is maintained by the National Library of Medicine.
      • The National Organization for Rare Disorders (NORD) has a report for patients and families about this condition. NORD is a patient advocacy organization for individuals with rare diseases and the organizations that serve them.

        In-Depth Information

        • 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.
        • Orphanet is a European reference portal for information on rare diseases and orphan drugs. Access to this database is free of charge.
        • PubMed is a searchable database of medical literature and lists journal articles that discuss Sickle beta thalassemia. Click on the link to view a sample search on this topic.

          References

          1. MA Bender, MD, PhD and Gabrielle Douthitt Seibel, MN, MPH, ARNP. Sickle Cell Disease. GeneReviews. October 2014; https://www.ncbi.nlm.nih.gov/books/NBK1377/.
          2. Sickle Cell Disease. Genetics Home Reference. August 2012; https://www.ghr.nlm.nih.gov/condition/sickle-cell-disease.
          3. Sickle Cell Disease. NORD. April 2008; https://www.rarediseases.org/rare-disease-information/rare-diseases/byID/25/viewAbstract.
          4. Elliott P Vichinsky, MD. Variant sickle cell syndromes. UpToDate. March 2014;
          5. Joseph E Maakaron, MD. Sickle Cell Anemia. Medscape Reference. September 2014; https://emedicine.medscape.com/article/205926-overview.

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