9 Things to Know About the Inheritance of Friedreich’s Ataxia

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by Wendy Henderson |

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Friedreich’s ataxia is an inherited disease that affects movement and coordination. It’s a progressive disease with symptoms including loss of strength, weakened muscles, spasticity, impaired speech, hearing and vision problems, and in some cases, diabetes and scoliosis.

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Here are some important facts about the inheritance of Friedreich’s ataxia according to Friedreich Ataxia News and the Muscular Dystrophy Association:

  • The condition is due to mutations in the frataxin (FXN) gene.
  • Friedreich’s ataxia is an autosomal recessive disease which means that a person inherits a copy of the mutated FXN gene from both their mother and father.
  • If both the mother and father are carriers of the mutated FXN gene there is a one in four chance that any of their children will develop Friedreich’s ataxia, a one in two chance they will not develop the disease but will become a carrier, and a one in four chance they will neither develop the disease nor become a carrier.
  • Part of the FXN gene contains a series of three DNA building blocks (two adenines and one guanine) called a GAA trinucleotide repeat. In people without the condition, this is repeated between five and 33 times. In those with the condition, this sequence is repeated between 66 to 1,000 times and known as a “repeat expansion.”
  • The number of times this sequence is repeated is related to the age of onset, the severity of the condition, and how quickly it progresses.
  • People with fewer than 300 GAA trinucleotide repeats tend to have a later onset of the disease, usually presenting symptoms after the age of 25.
  • It’s estimated that one in 100 people in the U.S. is a carrier of Friedreich’s ataxia.
  • People of Cajun (Acadian) descent are slightly more at risk of the disease, with one in 70 being carriers.
  • More than 95 percent of people with Friedreich’s ataxia have repeated expansions on both FXN genes. The rest of cases have one FXN gene with a repeat expansion and one with a single letter alteration to the DNA code called a point mutation.

MORE: Five types of treatment for Friedreich’s ataxia

Friedreich’s Ataxia News is strictly a news and information website about the disease. It does not provide medical advice, diagnosis or treatment. This content is not intended to be a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or another qualified health provider with any questions you may have regarding a medical condition. Never disregard professional medical advice or delay in seeking it because of something you have read on this website.