Amyloidosis, hereditary, transthyretin-related

Causes

Why does hereditary transthyretin amyloidosis happen?

Hereditary transthyretin amyloidosis is caused by gene changes in the TTR gene. Our genes contain instructions for how our bodies grow and develop in what is called DNA. Genes are inherited from our parents and passed on to our children. Genes make 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.

Changes (or mutations) in the TTR gene cause hereditary transthyretin amyloidosis, and can be associated with very different symptoms of the condition. Gene mutations are passed from parent to child in an autosomal dominant pattern. This means that someone with a TTR gene mutation has a 50/50 chance to pass it to their sons or daughters (and a 50/50 chance not to), with each child. No parent has control over which genes they pass/don't pass to their children.

To learn more about how hereditary transthyretin amyloidosis runs in families, speak to your doctor or look into a referral to see a genetic counselor. In the U.S., you can find a genetic counselor near you by searching the Find a Genetic Counselor website (from the National Society of Genetic Counselors) at http://www.nsgc.org/findageneticcounselor.

References
  • Obici L, Kuks JB, Buades J, et al. Recommendations for presymptomatic genetic testing and management of individuals at risk for hereditary transthyretin amyloidosis. Curr Opin Neurol. 2016;29 Suppl 1:S27-35.
  • Amyloidosis, transthyretin-related, hereditary. Online Inheritance in Man (OMIM) website. http://www.omim.org/entry/105210
  • Gorevic PD. Genetic factors in amyloidosis diseases. UpToDate Inc. http://www.uptodate.com/contents/genetic-factors-in-the-amyloid-diseases
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How does the gene change cause symptoms in hereditary transthyretin amyloidosis?

Does anything besides genetics cause hereditary transthyretin amyloidosis?

How does the gene change cause symptoms in hereditary transthyretin amyloidosis?

Hereditary transthyretin amyloidosis is caused by changes (mutations) in the TTR gene. The TTR gene usually makes a protein. This protein moves other substances through the body, specifically vitamin A and thyroxine (a thyroid hormone). When proteins are made, they are "folded" into a specific shape. A mutation in the TTR gene causes transthyretin to be "misfolded" and abnormally shaped. The misfolded transthyretin proteins will clump together and form amyloid deposits. The abnormal transthyretin cannot perform its transporter job. In addition, the misfolded proteins start to build up in tissues and organs of the body. The misfolded proteins begin to merge together to form small or slender fibers called fibrils. When enough of the misfolded proteins (called amyloid) build up, they will damage the surrounding tissues and organs. The nerves, heart, kidneys, and gastrointestinal tract are commonly affected in people.

References
Does anything besides genetics cause hereditary transthyretin amyloidosis?

Amyloidosis may occur for reasons beyond genetics and gene changes (or mutations). Hereditary transthyretin amyloidosis is caused by mutations in the TTR gene. Several mutations have been found in the TTR gene. A specific mutation may be more likely to cause certain symptoms. Researchers have also learned that many genetic disorders are influenced by environmental factors and changes in other genes (called modifier genes). Scientists are trying to figure out how different changes in the TTR gene can lead to different forms of hereditary transthyretin amyloidosis and to determine whether anything else can influence how the disorder develops in a person.

References

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