Friedreich's ataxia

Definition

Friedreich's ataxia is a rare disease passed down through families (inherited) that affects the muscles and heart.

Alternative Names

Spinocerebellar degeneration

Causes, incidence, and risk factors

Friedreich's ataxia is caused by a defect in a gene called Frataxin (FXN), which is located on chromosome 9. Changes in this gene cause the body to produce too much of part of DNA called trinucleotide repeat (GAA). Normally, the body contains about 8 to 30 copies of GAA. Those with Individuals with Friedreich's ataxia have as many as 1,000 copies. The more copies of GAA a patient has, the earlier in life the disease starts and the faster it gets worse.

Friedreich's ataxia is an autosomal recessive genetic disorder. This means you must get a copy of the defective gene from both your mother and father.

About 1 in every 22,000-29,000 develop this disease. Family history of the condition raises your risk.

Symptoms

Symptoms are caused by the wearing away of structures in areas of the brain and spinal cord that control coordination, muscle movement, and some sensory functions. Symptoms generally begin in childhood before puberty, and may include:

• Abnormal speech
• Changes in vision, particularly color vision
• Decrease in ability to feel vibrations in lower limbs
• Foot problems, such as hammer toe and high arches
• Hearing loss -- occurs in about 10% of patients
• Jerky eye movements
• Loss of coordination and balance, which leads to frequent falls
• Muscle weakness
• No reflexes in the legs
• Unsteady gait and uncoordinated movements (ataxia) -- gets worse with time

Muscle problems lead to changes in the spine, which may result in scoliosis or kyphoscoliosis.

Heart disease usually develops and may lead to heart failure. Death may result from heart failure or dysrhythmias that do not respond to treatment. Diabetes may develop in later stages of the disease.

Signs and tests

The following tests may be performed:

• ECG
• Electrophysiological studies
• EMG (electromyography)
• Genetic testing for the frataxin gene
• Nerve conduction tests
• Muscle biopsy
• X-ray, CT scan, or MRI of the head
• X-ray of the chest
• X-ray of the spine

Tests of the heart may show a condition called hypertrophic cardiomyopathy in about 66% of persons with this condition.

Blood sugar (glucose) tests may reveal diabetes or glucose intolerance. An eye exam may show damage to the optic nerve, which usually occurs without symptoms.

Treatment

Treatment for Friedreich's ataxia includes:

• Counseling
• Speech therapy
• Physical therapy
• Walking aids or wheelchairs

Orthopedic interventions (such as braces) may be needed for scoliosis and foot problems. Treatment of heart disease and diabetes may help improve the quality and duration of life.

Expectations (prognosis)

Friedreich's ataxia slowly gets worse and causes problems performing everyday activities. Most patients need to use a wheelchair within 15 years of the disease's start. The disease may lead to early death.

Complications

• Diabetes
• Heart failure or heart disease
• Loss of ability to move around

Calling your health care provider

Call your health care provider if muscle weakness, numbness, loss of coordination, loss of reflexes, or other symptoms of Friedreich's ataxia occur (particularly if there is a family history of the disorder).

Prevention

Individuals with a family history of Friedreich's ataxia who intend to have children should consider genetic screening and counseling to determine their risk.

References

Johnston MV. Movement disorders. In: Kliegman RM, Behrman RE, Jenson HB, Stanton BF, eds. Nelson Textbook of Pediatrics. 18th ed. Philadelphia, Pa: Saunders Elsevier; 2007:chap 597.