Genetics and Ataxia

hereditary ataxia - where symptoms develop slowly over many years and are caused by faulty genes that a person inherits from their parents; the most common type is Friedreich's ataxia

Source: NHS Choices UK1

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Hereditary ataxia is caused by a faulty gene passed on by family members, who may or may not be affected.

Source: NHS Choices UK2

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Friedreich's ataxia is the most common type of hereditary ataxia (caused by genes you've inherited).

Source: NHS Choices UK3

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There are two ways that ataxia can be inherited:

These are described in more detail in the following sections.

Autosomal recessive

When ataxia is autosomal recessive, it means the affected person has inherited the mutated gene from both their mother and their father.

If they only received one mutated gene from either parent, the other normal gene will cancel out the effects of the faulty gene and they will be a carrier of the condition. This means they don't have the condition themselves, but could pass it on to their children if their partner is also a carrier of the faulty gene.

It's estimated around 1 in every 85 people are carriers of the mutated gene that causes Friedreich's ataxia, and around 1 in every 100 people are carriers of the mutated gene that causes ataxia-telangiectasia.

If two carriers of the mutated gene were to have a baby, there would be a:

  • one in four chance the baby would receive a pair of normal genes
  • one in two chance the baby would receive one normal gene and one mutated gene (be a carrier)
  • one in four chance the baby would receive a pair of mutated genes and develop ataxia

If you have autosomal recessive ataxia and your partner is a carrier, there is a one in two chance your baby will receive one normal gene and one mutated gene and will be a carrier, and a one in two chance your baby will receive a pair of mutated genes and develop ataxia.

If you have autosomal recessive ataxia and your partner doesn't and they aren't a carrier, there's no risk of any of your children developing ataxia. This is because your mutated gene will be cancelled out by your partner's normal gene. Your children will be carriers, however.

Autosomal dominant

When ataxia is autosomal dominant, you can develop the condition if you receive a single faulty gene, either from your mother or father. This is because the mutation is strong enough to override the other normal gene.

If you have autosomal dominant ataxia, any children you have will have a one in two chance of developing ataxia.

Source: NHS Choices UK4

Genetic Testing for Ataxia

Genetic testing

Genetic testing involves taking a sample of blood and testing the DNA in it for any genetic mutation known to cause ataxia.

Currently, tests can detect the mutations responsible for Friedreich's ataxia, ataxia-telangiectasia and most of the spinocerebellar ataxias.

Source: NHS Choices UK5

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References

  1. Source: NHS Choices UK: nhs.uk/ conditions/ Ataxia/ 
  2. ibid.
  3. Source: NHS Choices UK: nhs.uk/ conditions/ ataxia/ symptoms/ 
  4. Source: NHS Choices UK: nhs.uk/ conditions/ ataxia/ causes/ 
  5. Source: NHS Choices UK: nhs.uk/ conditions/ ataxia/ diagnosis/ 

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Note: This site is for informational purposes only and is not medical advice. See your doctor or other qualified medical professional for all your medical needs.