Triple Repeat Disorder

F A is known as a triplet repeat disorder since it is caused by an expanded trinucleotide repeat. In those affected with F A, there are significantly more GAA repeats in the first intron of the FXN gene (see below). If repeat number exceeds 100, protein output is affected with an insufficient amount of the frataxin protein made. Low frataxin protein levels lead to dysfunction in mitochondria and the symptoms associated with F A. Often, more severe symptoms and earlier age of onset are seen as the number of repeats increases. Alternatively, a point mutation in the FXN gene can also reduce the amount of frataxin that is produced.