Friedreich Ataxia (FA)

 

 

Friedreich’s Ataxia (FA) is an autosomal recessive diseases with prevalence of 1 in 50,000 with a deduced carrier frequency of 1 in 120 in European population and is the most common hereditary ataxia. FA is a degenerative disease that involves the central and peripheral nervous system and the heart, and characterized by progressive gait and limb ataxia, a lack of tendon reflexes in the legs, loss of position sense, dysarthria, and pyramidal weakness of the legs. The age of onset is usually around puberty, and mostly before age 25. Most patients are confined to a wheelchair by their late 20s, and there is no treatment to slow the progression of the disease.

 

Molecular basis

The mutated gene in FA has been mapped to chromosome 9q13-q21.1. The gene is called X25 and identified in the critical region for the FA locus on 9q13. The gene encodes a 210 amino acid protein, frataxin. Point mutations were found in a few FA patients but the majority were homozygous for an unstable GAA trinucleotide expansion in the first X25 intron.

The trinucleotide repeat, which is present 7-34 times in normal individuals, expands to 66 repeats or greater in FA patients. To date alleles between the normal and abnormal ranges have not been found.

 

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