Friedreich's ataxia is the most common of the early-onset hereditary ataxias. It is an autosomal recessive, trinucleotide repeat disorder characterised by a GAA repeat in the X25 gene on chromosome 9 (frataxin). Friedreich's ataxia is unusual amongst trinucleotide repeat disorders in not demonstrating the phenomenon of anticipation.


  • Incidence: 0.03 cases per 100,000 person-years
  • Peak incidence: 6-15 years
  • Sex ratio: 1:1
<1 1-5 6+ 16+ 30+ 40+ 50+ 60+ 70+ 80+

Clinical features

The typical age of onset is 10-15 years old. Gait ataxia and kyphoscoliosis are the most common presenting features.

Neurological features
  • absent ankle jerks/extensor plantars
  • cerebellar ataxia
  • optic atrophy
  • spinocerebellar tract degeneration

Other features
  • hypertrophic obstructive cardiomyopathy (90%, most common cause of death)
  • diabetes mellitus (10-20%)
  • high-arched palate

Differential diagnosis

Comparison of Friedreich's ataxia and ataxic telangiectasia. Note in particular how ataxic telangiectasia tends to present much earlier, often at the age of 1-2 years