Hereditary hemorrhagic telangiectasia

Causes

What gene changes cause hereditary hemorrhagic telangiectasia?

Hereditary hemorrhagic telangiectasia (HHT) is caused by gene changes in one of at least four different genes. People have about 20,000-25,000 genes in their bodies. Our genes contain our body's genetic information, called DNA; genes are segments of DNA found on chromosomes. Genes are inherited from our parents and passed on to our children. Genes are like our body's instruction manual - they control the growth, development and normal function of the body. Genes produce specific proteins that the body needs to grow and work properly. When there is an unexpected change in a gene, the protein that the gene produces may be absent or not work properly.

HHT can be caused by alterations (mutations) in the ACVRL1, ENG, GDF2, or SMAD4 genes. More than 600 different mutations have been identified in these four genes. A mutation in any of these four genes leads to problems with the formation of blood vessels, a process called angiogenesis.

Most people have a change in the ACVRL1 gene or the ENG gene. Some people do not have a change in any of these four genes and researchers believe that there is at least one more, as-yet-unidentified, gene that causes HHT.

To find a medical professional nearby who can discuss information about gene changes in HHT, a listing of medical geneticists can be found at the American College of Medical Geneticists website and genetic counselors can be found on the National Society of Genetic Counselors website.

References
  • McDonald J, Pyeritz RE. Hereditary Hemorrhagic Telangiectasia. GeneReviews website. Accessed February 23, 2017. https://www.ncbi.nlm.nih.gov/books/NBK1351/
  • Hereditary hemorrhagic telangiectasia. Genetics Home Reference website. Accessed February 23, 2017. https://ghr.nlm.nih.gov/condition/hereditary-hemorrhagic-telangiectasia
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How does the gene change cause symptoms in hereditary hemorrhagic telangiectasia?

How does the gene change cause symptoms in hereditary hemorrhagic telangiectasia?

Hereditary hemorrhagic telangiectasia (HHT) can be caused by alterations (mutations) in the ACVRL1, ENG, GDF2, or SMAD4 genes. More than 600 different mutations have been identified in these four genes. A mutation in any of these four genes leads to problems with the formation of blood vessels, a process called angiogenesis.

Our genes contain our body's genetic information, called DNA; genes are segments of DNA found on chromosomes. Genes are inherited from our parents and passed on to our children. Genes are like our body's instruction manual - they control the growth, development and normal function of the body. Genes produce specific proteins that the body needs to grow and work properly. When there is an unexpected change in a gene, the protein that the gene produces may be absent or not work properly.

Because of these gene mutations, people with HHT may lack normal capillaries. These tiny blood vessels connect arteries (blood vessels that carry blood away from the heart) to the veins (blood vessels that carry blood to the heart). Without normal capillaries, arteries and veins are connected directly. These abnormal connections are fragile and often rupture causing bleeding.

References
  • Hereditary hemorrhagic telangiectasia. Genetics Home Reference website. Accessed February 23, 2017. https://ghr.nlm.nih.gov/condition/hereditary-hemorrhagic-telangiectasia
  • Hereditary hemorrhagic telangiectasia. The National Organization for Rare Disorders website. Accessed February 23, 2017. https://rarediseases.org/rare-diseases/hereditary-hemorrhagic-telangiectasia/

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