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Genetic Testing for Ataxia?

Hereditary forms of ataxia are often suspected when there is a family history of ataxia, or if the age of onset is very young. There are two types of genetic changes that can cause ataxia:

  • Repeat expansions-Some parts of our genetic code contain repeated letters of DNA sequence. If there are too many of these repeats, then the gene may begin to malfunction and cause ataxia. Ataxias that are caused by abnormal numbers of DNA repeats include: SCA1, SCA2, SCA3, SCA6, SCA7, SCA8, SCA10, SCA12, SCA17, Friedreich ataxia, and DRPLA.
  • DNA sequence changes-Some types of ataxia are caused by single-letter misspellings in the genetic code. For these types of ataxia, laboratories need to examine all of the letters of the genetic code to see if there is a spelling change. The types of ataxia that are diagnosed by DNA sequence change include: SCA5, SCA13, SCA14, AOA1, AOA2, Ataxia with vitamin E deficiency and others.
  • "Variance of unknown significance": Some gene tests (especially SCA 14 gene) may show a "variation of unknown significance". It is important that these types of results be interpreted very carefully because they do not mean that the individual has SCA14 in most cases.

Interpreting the results of genetic testing

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