Huntington's Disease

What is Huntington's disease?

Huntington’s disease is a progressive condition in which some parts of the brain malfunction. It is rare for a patient with Huntington’s to live for more than 20 years past their diagnosis as the brain damage gets worse over time. Movement, cognition, mental health, memory and judgement are all affected by this devastating illness.¹ The name ‘Huntington’s disease’ came about as a result of the American physician George Huntington who, at age 22, wrote a clinical description called ‘On Chorea’, published in 1872, of the disease that is now known as Huntington’s.²

Symptoms of Huntington's disease

The onset of symptoms usually occurs between the ages of 30-50. However, there are also cases of juvenile Huntington’s - occurring in people below the age of 20; this is very rare.³ The condition is progressive, meaning that once the symptoms have started, they continue to worsen.

Early symptoms often experienced include:

• Lapses in memory and difficulty concentrating
• Depression; a change in mood and unusually aggressive behaviour
• General clumsiness; this could include dropping things and stumbling

In cases of juvenile Huntington’s disease, noticeable changes in a young person are seen, such as a very quick decline in their school ability, and problems with movement can occur early on.

As the disease progresses, symptoms can include:⁴

• Swallowing problems
• Increasingly slow and rigid movements
• Breathing problems
• Personality change- this can be so profound that it is difficult to recognise the person as somebody that you once knew
• Difficulty with sitting and standing
• Involuntary twitching and jerking movements (chorea)
• Difficulty speaking
• Memory problems

In the latest stages of the disease, around-the-clock nursing care is needed as daily activity will become impossible. 

Causes of Huntington's disease

Huntington’s disease is caused by a faulty gene and therefore is an inherited condition.  The gene involved is called huntingtin, a gene attached to chromosome number 4. The role of the huntingtin gene is to produce huntingtin protein which is essential for neuronal function and the body’s development pre-birth.⁵

A faulty huntingtin gene produces repeat genetic sequences called CAG in certain parts of the protein which leads to damaged neurons. There is need for more research to find the exact way in which this happens and why it occurs. The parts of the brain that are affected by this mutation are the basal ganglia; mainly responsible for motor functions, and the cerebral cortex; mainly responsible for higher-level processing such as memory and personality. When the cells in this part of the brain become damaged, the symptoms of Huntington’s become apparent. 

Who is more likely to get Huntington's disease?

The Huntington’s gene is dominant; this means that people with the faulty gene will develop the disease at some point, although it is impossible to know when. Because half of a person’s genes are inherited from their mother and half from their father, every child that is the offspring of a parent that carries the Huntington’s gene has a 50% chance of inheriting it.

This also means that there is a 50% chance of not getting the disease.

Complications

Often patients with Huntington’s develop other conditions such as pneumonia, and can suffer injuries because of falls and complications resulting from the inability to swallow.

There’s also an increased risk of mood disorders such as depression which is understandable because the individual gradually loses the ability to function. Furthermore, when a person is diagnosed with Huntington’s, the risk of death by suicide is increased.⁶

Prevention

There is no way to prevent Huntington’s disease from developing in somebody that has the mutated gene. Some people with a family history of the disease may choose to undergo genetic testing to uncover whether they also have a faulty copy of the gene. A simple blood test is carried out and the DNA within it is examined to count the number of CAG repeats in the huntingtin gene. Individuals with Huntington’s usually have more than 40 repeats whilst those unaffected have 28 or less. In more recent years, there has been a test to determine if an unborn foetus carries the Huntington’s gene.⁷ 

Genetic testing is not to be taken lightly, and it is recommended that genetic counselling is carried out before testing. Some people might choose not to know whether they carry the gene or not, because knowledge of this  means that they know what difficulties lie ahead for them. On the other hand, awareness can also help people prepare for their future.

Treatment and support

There are currently no treatments available to treat Huntington’s disease and unfortunately, the progression cannot be slowed down. However, some medications can reduce the burden of some aspects of the disease to improve quality of life. Huntington’s disease news lists several medications such as Haloperidol to reduce involuntary movements and chorea, and Seroquel to potentially reduce psychiatric symptoms. Speech and language therapy are also important to help with communication, and occupational therapy can help put adaptations in place that might be needed.⁸

There are organisations such as the Huntington’s Disease Association that provide support and advice for those affected by the disease. The association contributes a wealth of information for all of those involved in the life of a patient with Huntington’s. They also provide research information,  and advice on financial and emotional services that can help a patient and their loved ones. 

When to seek medical attention

If a patient knows that Huntington’s disease runs in their family, it would be a good idea to get medical attention as soon as possible to get a better understanding of the disease and the likelihood that they will develop it. A GP should be able to discuss the options for genetic testing and counselling along with any concerns that the patient has. 

Likewise, any symptoms that a patient might experience should be discussed with a medical professional straight away. 

Summary

Huntington’s disease is a devastating ailment that gradually reduces an individual’s functional ability until they, unfortunately, pass away. Symptoms usually begin around age 30, however, juvenile Huntington’s also occurs. 

Huntington’s is caused by an inherited dominant mutation of the huntingtin gene which is passed down by a parent. There is no way to slow down or prevent the condition but there are medications that can be used to increase the quality of life and reduce some of the associated symptoms. Support organisations are available to ensure that patients and their loved ones have access to assistance when required.. 

References

1. Huntington’s disease [Internet]. [cited 2023 Feb 10]. Available from: https://www.nhsinform.scot/illnesses-and-conditions/brain-nerves-and-spinal-cord/huntingtons-disease
2. History of Huntington’s disease - Huntington’s disease society of America [Internet]. 2017 [cited 2023 Feb 10]. Available from: https://hdsa.org/what-is-hd/history-and-genetics-of-huntingtons-disease/history-of-huntingtons-disease/
3. Huntington’s disease [Internet]. [cited 2023 Feb 10]. Available from: https://www.nhsinform.scot/illnesses-and-conditions/brain-nerves-and-spinal-cord/huntingtons-disease
4. Huntington’s disease - Symptoms [Internet]. NHS. UK. 2018 [cited 2023 Feb 10]. Available from: https://www.nhs.uk/conditions/huntingtons-disease/symptoms/
5. Huntington’s disease association [Internet]. Huntington's Disease Association. [cited 2023 Feb 10]. Available from: https://www.hda.org.uk/huntingtons-disease/what-is-huntingtons-disease/what-causes-huntingtons-disease
6. Duijn E van, Fernandes AR, Abreu D, Ware JJ, Neacy E, Sampaio C. Incidence of completed suicide and suicide attempts in a global prospective study of Huntington’s disease. BJPsych Open [Internet]. 2021 Sep [cited 2023 Feb 10];7(5):e158. Available from: https://www.cambridge.org/core/journals/bjpsych-open/article/incidence-of-completed-suicide-and-suicide-attempts-in-a-global-prospective-study-of-huntingtons-disease/40392EBF4B6FBEC97B52470FAF568A82
7. About Huntington’s disease [Internet]. Genome.gov. [cited 2023 Feb 10]. Available from: https://www.genome.gov/Genetic-Disorders/Huntingtons-Disease
8. Huntington’s disease [Internet]. [cited 2023 Feb 10]. Available from: https://www.nhsinform.scot/illnesses-and-conditions/brain-nerves-and-spinal-cord/huntingtons-disease

This content is purely informational and isn’t medical guidance. It shouldn’t replace professional medical counsel. Always consult your physician regarding treatment risks and benefits. See our editorial standards for more details.

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Jessica Gibson

Bachelor of Science- BSc(Hons)- Health Sciences- The Open University

Jessica is a Health Sciences graduate with a passion for both Science and English and is delighted to have found a way to combine the two. She is a motivated and enthusiastic writer determined to make scientific information more widely accessible.
Jessica is especially interested in infectious diseases, neurodegenerative diseases, the impact of trauma on physical health, health equity and the health of children residing in developing nations.

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