Huntington disease

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Huntington disease (HD) is an inherited disease that causes certain nerve cells in the brain to die. People are born with the gene that causes HD, but symptoms don’t usually appear until mid-adulthood.

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Overview

Huntington disease (often shortened to HD) is an inherited disease that causes certain nerve cells in the brain to die. People are born with the gene that causes HD, but symptoms don’t usually appear until mid-adulthood. If a parent has HD, their children will have a 50% chance of inheriting the gene.

As HD progresses, physical, emotional and cognitive functioning will be affected as the person with HD becomes less able to control movements, recall events, make decisions and control emotions.

Other names

Other names historically used for HD include:

  • Chorea,
  • Chronic Progressive Chorea,
  • Huntington’s Chorea, and
  • Hereditary Chorea.

The word “Chorea” (a Greek term for dance) is used to describe the involuntary movements that people with HD commonly experience.

Symptoms

The age of symptom onset and the rate of the disease progression vary among people living with HD. However, symptoms of HD typically begin in people between the ages of 30 and 50, and usually progress over a 10- to 25-year period.

Changes in cognitive abilities

Early symptoms of HD often include subtle cognitive changes. Slight physical changes may also develop at this stage; for example, a person may experience an increased difficulty controlling their movements.

Changes in mood and personality

As the disease progresses, it is not uncommon for a person with HD to experience personality changes such as irritability, depression and mood swings.

Changes in judgement and memory

A person with HD may experience trouble with memory, concentration, learning new things or making decisions.

Obsessive-compulsive behaviour

Obsessive-compulsive behaviour, such as continually repeating the same activity, is also a common feature of HD.

Changes in physical abilities

The initial physical symptoms will gradually develop into more obvious involuntary movements such as jerking and twitching of the head, neck, arms and legs. The later stage symptoms of HD may include an increased difficulty with walking, eating independently and swallowing. Other symptoms at this stage may include an increased difficulty with concentration and communication.

Diagnosis

Medical history and exams

A thorough assessment will often include:

  • Physical exams,
  • Neurological exams,
  • Psychiatric exams, and
  • A review of the person’s complete family medical history to help rule out other conditions.

Changes in behaviour and personality, like increased irritability, can be mistaken for other conditions, causing some of the early symptoms of HD to be initially overlooked.

Genetic testing

People may undergo genetic testing via a blood test to confirm or rule out HD if they are exhibiting symptoms of the disease. Brain imaging (MRI) is not usually needed but may be requested by a physician to detect any structural changes in the parts of the brain that are affected by HD or to rule out other conditions.

Predictive genetic testing is also available for adults who are not currently showing signs of HD, but who have a strong family history of the disease. In this case, a result of ‘gene positive’ or ‘gene negative’ is given, but a diagnosis of HD is not given until symptoms develop – usually much later in life.

Prior to going through predictive testing, it's important that the person speak with a genetic counselor to discuss both the advantages and disadvantages of genetic testing.

Risk factors

Huntington disease is a familial disease, passed from parent to child through a mutation in the normal gene that is responsible for the huntingtin protein.

Anyone with a parent with HD has a 50% chance of inheriting the gene, and everyone who inherits the gene will eventually develop the disorder. In about one to three percent of cases, no history of the disease can be found in other family members.

Treatment

Medications can help manage some symptoms, but cannot slow down or stop the disease. As a result, there is currently no cure for HD.

On a promising note, there are several drug trials underway, which may bring new treatment approaches forward.

Therapeutic approaches

Therapeutic approaches also support people living with HD to manage symptoms of their disease.

  • Occupational therapy can help improve the functional ability of people living with HD through the use of assistive devices, while physical therapy can help maintain physical abilities.
  • Since HD can impair the muscle control needed for eating and speaking, speech therapy can help improve a person’s verbal communication and can address eating and swallowing challenges.

It's important that caregivers and professionals work together to help manage the most effective treatment for each individual, since the disease develops differently in different people, even within the same family or generation.

More information and resources

https://www.huntingtonsociety.ca/

Huntington Society of Canada. The Huntington Society of Canada offers ongoing support, education and information to help improve quality of life for Canadians impacted by Huntington disease.