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.

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

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

See:

Telangiectasia