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Diseases

Genetic and Rare Diseases Information Center (GARD)

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Friedreich ataxia


Other Names for this Disease
  • FRDA
  • Friedreich's ataxia
  • Hereditary spinal ataxia
  • Hereditary spinal sclerosis
  • Spinocerebellar ataxia, Friedreich
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Cause


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What causes Friedreich ataxia?

Friedreich ataxia is caused by a defect in a gene called Frataxin (FXN), which provides instructions for making a protein called frataxin. One region of the FXN gene contains a segment of DNA known as a GAA trinucleotide repeat. This segment is made up of a series of three DNA building blocks (one guanine and two adenines) that appear multiple times in a row. Normally, this segment is repeated 5 to 33 times within the FXN gene. In people with Friedreich ataxia, the GAA segment is repeated 66 to more than 1,000 times. The length of the GAA trinucleotide repeat appears to be related to the age at which the symptoms of Friedreich ataxia appear.[1]

The abnormally long GAA trinucleotide repeat disrupts the production of frataxin, which severely reduces the amount of this protein in cells. Certain nerve and muscle cells cannot function properly with a shortage of frataxin, leading to the characteristic signs and symptoms of Friedreich ataxia.[1]
Last updated: 1/23/2012

References
  1. Friedreich ataxia. Genetics Home Reference. May 2010; http://ghr.nlm.nih.gov/condition/friedreich-ataxia. Accessed 1/23/2012.