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Friedreich’s Ataxia


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What is the disease?


Friedreich’s Ataxia is caused by an inherited genetic mutation. The mutated gene, FXN must be inherited by autosomal recessive transmission. Autosome refers to the placement of the FXN gene (chromosome 9, which is one of the twenty-two pairs of autosomes). Recessive means that an individual must inherit two copies of this gene for them to develop symptoms. If an individual receives the defective gene from only one parent then they will not develop symptoms but they will be a carrier. Individuals who have a family history of the disease are more susceptible to get it.


The gene (FXN) is responsible for producing 33 copies of a specific DNA sequence (GAA), however, a mutated gene may cause the DNA sequence to repeat from 66 to 1000 times. This unusual production of the DNA sequence greatly affects the cerebellum and the spinal cord.


A mutation in the FXN gene causes an accumulation of iron in the mitochondria. Iron is essential for the mitochondria as it is used to make certain genes and act as an electron donor/acceptor in the ETC. However, an accumulation of iron can cause oxidative stress (an imbalance in free radicals and antioxidants) which is harmful to mitochondrial function. Since cells rely on mitochondria for energy, defective mitochondria can severely damage cells. Damaged cells lead to damaged organs, and damaged organs lead to damaged biological systems. This is why the occurrence of Friedreich’s Ataxia is related to damage in the parts of the nervous system, and heart among other organs.


Symptoms


Friedreich’s Ataxia can be diagnosed anywhere between the age of 2 to the early 50s. This being said, it is usually diagnosed between pre-teens to mid-teens (ages 10 to 15). During this time is when individuals begin to experience symptoms, however on rare occasions (25% of the time), individuals begin experiencing symptoms after they are 25 years old.


Friedreich’s Ataxia affects the cerebellum, a part of the brain that is responsible for various functions such as balance, and coordination, and is also responsible for voluntary movement coordination. Therefore, the disease causes the affected individual to have poor balance and coordination. In addition to that, the disease also induces a gradual loss of strength, a loss of control over limb movement, and eventually not being able to feel (losing sensation in) their arms and legs. Due to the disease’s impact on muscle coordination, affected individuals can also have impaired speech, hearing loss and issues with vision. Friedreich’s Ataxia patients also usually require a wheelchair approximately 10 years after developing symptoms. In addition to this, individuals may also develop scoliosis (an abnormal curvature of the spine). Patients may also develop other complications such as diabetes or heart disease. As a matter of fact, around 75% of Friedreich’s Ataxia patients develop heart abnormalities as the disease worsens. The common symptoms of heart disease include heart palpitations, pain in the chest, and dizziness (amongst other symptoms). The most common type of heart disease patients develop is hypertrophic cardiomyopathy which is characterized by the thickening of the cardiac muscle.


Summary of Symptoms

  • Poor balance and coordination.

  • Gradual loss of strength.

  • Loss of control over limb movement.

  • Lost sensation in arms and legs.

  • Impaired speech.

  • Hearing loss.

  • Vision issues.

  • Development of scoliosis.

  • Development of complications such as diabetes or heart disease.


Treatments


A cure for Friedreich’s Ataxia and other mitochondrial diseases has yet to be found. However, doctors may help manage symptoms by prescribing physical and speech therapy. In order to manage physical symptoms such as scoliosis, patients may require braces, walking aids, or even surgery.


Overall, the treatment for Friedreich’s Ataxia is focused on targeting the symptoms. For complicated symptoms, doctors prescribe medication. For heart disease, doctors prescribe drugs such as ACE inhibitors (lower blood pressure by relaxing veins and arteries), diuretics (increase the amount of water and salt removed from the body in the urine), and beta-blockers (help reduce blood pressure). Doctors can also suggest the use of pacemakers to regulate irregular heartbeat. In order to manage diabetes, doctors may prescribe insulin which helps control the amount of glucose (blood sugar) in the bloodstream. For symptoms of scoliosis, doctors may suggest surgery. A common example of scoliosis surgery is spinal fusion. This surgery involves the straightening of the spine with the help of rods and screws and then placing small pieces of bone over the spine that fuse with it and help it retain its normal shape and function. This being said, unfortunately, there is no treatment for the muscle weakness caused by this disease. However, physical therapy, such as speech therapy may help the tongue and facial muscles and improve speech and ease swallowing.


Summary of Treatments

  • Medication for complications such as ACE inhibitors for heart disease and insulin for diabetes.

  • Surgery for scoliosis.

  • Physical therapy (ex. speech therapy) for muscle weakness.


References


Delgado, A. (2021, February 19). Friedreich’s Ataxia. Healthline. https://www.healthline.com/health/friedreichs-ataxia

Friedreich’s Ataxia (FA) - Diseases. (2021, April 28). Muscular Dystrophy Association. https://www.mda.org/disease/friedreichs-ataxia

Friedriech’s Ataxia Research Alliance - Grant Program. (n.d.). Curefa. https://curefa.org/grant

Lafleur, M. (2019, January 28). Which Assistive Device(s). Friedreich’s Ataxia News Forums. https://friedreichsataxianews.com/forums/forums/topic/which-assistive-devices/



Article Author: Twisha Bhatt

Article Editors: Victoria Huang, Sherilyn Wen