Friedreich Ataxia

Synonyms

6

Overview

Friedreich's ataxia  is a common form of inherited ataxia. In most cases, symptoms appear before the age of 25. Signs and symptoms of FA include a variety of neurological problems, cardiomyopathy, diabetes and scoliosis. Treatment for people with FA is usually directed at managing symptoms, as there is no cure.

It is a genetic condition that affects the nervous system and causes movement problems. People with this condition develop impaired muscle coordination (ataxia) that worsens over time. Other features of this condition include the gradual loss of strength and sensation in the arms and legs; muscle stiffness (spasticity); and impaired speech, hearing, and vision. Individuals with Friedreich ataxia often have a form of heart disease called hypertrophic cardiomyopathy, which enlarges and weakens the heart muscle and can be life-threatening. Some affected individuals develop diabetes or an abnormal curvature of the spine (scoliosis).

Most people with Friedreich ataxia begin to experience the signs and symptoms of the disorder between ages 5 and 15. Poor coordination and balance are often the first noticeable features. Affected individuals typically require the use of a wheelchair about 10 years after signs and symptoms appear.

About 25 percent of people with Friedreich ataxia have an atypical form in which signs and symptoms begin after age 25. Affected individuals who develop Friedreich ataxia between ages 26 and 39 are considered to have late-onset Friedreich ataxia (LOFA). When the signs and symptoms begin after age 40 the condition is called very late-onset Friedreich ataxia (VLOFA). LOFA and VLOFA usually progress more slowly than typical Friedreich ataxia.

Symptoms

Symptoms usually begin between the ages of 5 and 15 but can, on occasion, appear in adulthood or even as late as age 75. The first symptom to appear is usually difficulty in walking, or gait ataxia. The ataxia gradually worsens and slowly spreads to the arms and then the trunk. Over time, muscles begin to weaken and waste away, especially in the feet, lower legs, and hands, and deformities develop. Other symptoms include loss of tendon reflexes, especially in the knees and ankles. There is often a gradual loss of sensation in the extremities, which may spread to other parts of the body. Dysarthria (slowness and slurring of speech) develops, and the person is easily fatigued. Rapid, rhythmic, involuntary movements of the eye (nystagmus) are common. Most people with Friedreich's ataxia develop scoliosis (a curving of the spine to one side), which, if severe, may impair breathing.

Other symptoms that may occur include chest pain, shortness of breath, and heart palpitations. These symptoms are the result of various forms of heart disease that often accompany Friedreich ataxia, such as cardiomyopathy (enlargement of the heart), myocardial fibrosis (formation of fiber-like material in the muscles of the heart), and cardiac failure. Heart rhythm abnormalities such as tachycardia (fast heart rate) and heart block (impaired conduction of cardiac impulses within the heart) are also common. About 20 percent of people with Friedreich ataxia develop carbohydrate intolerance and 10 percent develop diabetes mellitus. Some people lose hearing or eyesight.

The rate of progression varies from person to person. Generally, within 10 to 20 years after the appearance of the first symptoms, the person is confined to a wheelchair, and in later stages of the disease individuals become completely incapacitated. Life expectancy may be affected, and many people with Friedreich ataxia die in adulthood from the associated heart disease, the most common cause of death. However, some people with less severe symptoms of Friedreich ataxia live much longer, sometimes into their sixties or seventies[

Symptoms:

  • Muscle weakness in the arms and legs
  • Loss of coordination Vision impairment
  • Hearing loss
  • Slurred speech
  • Curvature of the spine (scoliosis)
  • High plantar arches- pes cavus deformity of the foot
  • Diabetes Heart disorders (e.g., atrial fibrillation, and resultant tachycardia (fast heart rate) and hypertrophic cardiomyopathy)

Causes

Friedreich ataxia is caused by mutations in the FXN gene. This gene provides instructions for making a protein called frataxin. Although its role is not fully understood, frataxin is important for the normal function of mitochondria, the energy-producing centers within cells. One region of the FXN gene contains a segment of DNA known as a GAA trinucleotide repeat. This segment is made up of a series of three DNA building blocks (one guanine and two adenines) that appear multiple times in a row. Normally, this segment is repeated 5 to 33 times within the FXN gene. In people with Friedreich ataxia, the GAA segment is repeated 66 to more than 1,000 times. The length of the GAA trinucleotide repeat appears to be related to the age at which the symptoms of Friedreich ataxia appear.

The abnormally long GAA trinucleotide repeat disrupts the production of frataxin, which severely reduces the amount of this protein in cells. Certain nerve and muscle cells cannot function properly with a shortage of frataxin, leading to the characteristic signs and symptoms of Friedreich ataxia.

Friedreich ataxia is inherited in an autosomal recessive manner. This means that to be affected, a person must have a mutation in both copies of the responsible gene in each cell. The parents of an affected person usually each carry one mutated copy of the gene and are referred to as carriers. Carriers typically do not show signs or symptoms of the condition. When two carriers of an autosomal recessive condition have children, each child has a 25% (1 in 4) risk to have the condition, a 50% (1 in 2) risk to be a carrier like each of the parents, and a 25% chance to not have the condition and not be a carrier.

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.

Diagnosis

The list of diagnostic tests mentioned in various sources as used in the diagnosis of Friedreich's ataxia includes:

  • Physical exam
  • Electromyogram (EMG)
  • Genetic testing

Prognosis

Generally, within 15 to 20 years after the appearance of the first symptoms, the person is confined to a wheelchair, and in later stages of the disease, individuals become completely incapacitated. Most people with Friedreich's ataxia die in early adulthood if there is significant heart disease, the most common cause of death. Some people with less severe symptoms live much longer

Treatment

A person suffering from Friedreich's Ataxia may require some surgical interventions (mainly for the spine and heart). Often, titanium screws and rods are inserted in the spine to help prevent or slow the progression of scoliosis. As progression of ataxia occurs, assistive devices such as a cane, walker, or wheelchair are required for mobility and independence. Other assistive technology, such as a standing frame, can help reduce the secondary complications of prolonged use of a wheelchair. The goal of surgery is to keep the patient ambulatory as long as possible.

In many cases, patients experience significant heart conditions as well. These conditions are much more treatable, and are often countered with ACE inhibitors such as enalapril or lisinopril and other heart medications such as digoxin.

Persons with Friedreich’s ataxia may also benefit from a conservative treatment approach for the management of symptoms. Health professionals educated in neurological conditions, such as physical therapists and occupational therapists, can prescribe an exercise program tailored to maximize function and independence. To address the ataxic gait pattern and loss of proprioception typically seen in persons with Friedreich’s ataxia, physical therapists can use visual cueing during gait training to help facilitate a more efficient gait pattern. The prescription of an assistive device along with gait training can also prolong independent ambulation.

Low intensity strengthening exercises should also be incorporated to maintain functional use of the upper and lower extremities. Fatigability should be monitored closely. Stabilization exercises of the trunk and low back can help with postural control and the management of scoliosis. This is especially indicative if the person is non-ambulatory and requires the use of a wheelchair. Balance and coordination training using visual feedback can also be incorporated into activities of daily living. Exercises should reflect functional tasks such as cooking, transfers and self-care. Along with gait training, balance and coordination training should be developed to help minimize the risk of falls.

Stretching exercises can be prescribed to help relieve tight musculature due to scoliosis and pes cavus deformities.

Idebenone:

Idebenone, an antioxidant, was recently removed from the Canadian market in 2013 due to lack of effectiveness.

There is a Cochrane review on Antioxidants and other Pharmacological treatment in Friedreich Ataxia which was published in 2012 and is due to be updated before the end of 2015.

RG2833:

RG2833 is a histone deacetylase inhibitor originally developed by Repligen but later acquired by BioMarin Pharmaceutical in January 2014. The first human trials with this compound began in 2012.

Nicotinamide:

Nicotinamide administration on patients was associated with a sustained improvement in frataxin concentrations towards those seen in asymptomatic carriers during 8 weeks of daily dosing. The daily oral administration of nicotinamide at the doage of 3·8 g would result in a 1·5-times increase and 7·5 g in a doubling of frataxin protein concentration.

Speech Therapy:

Patients also often undertake speech therapy since dysarthria (a motor speech disorder) occurs in almost 100% of Friedreich's ataxia patients. Speech therapy seeks to improve speech outcomes and/or compensate for communication deficits.

In Research:

Studies by Horizon Pharma on the use of interferon gamma-1B for treatment was recently given fast track designation by the Food and Drug Administration

Resources

  • NIH
  • Mayo Clinic
  • Genetics Home Reference