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Huntington's disease

Huntington's disease is an inherited disorder that causes the degeneration of brain cells. This results in a progressive loss of the control of movement and mental ability, and changes in personality.

Around 4,800 people in the UK are living with Huntington's disease. It used to be called Huntington's chorea. Chorea means jerky, involuntary movements - a main symptom of the condition.

  • About Huntington's disease
  • Symptoms
  • Causes
  • Juvenile Huntington's disease
  • Treatment
  • Genetic tests
  • Pre-implantation Genetic Diagnosis (PGD)
  • Further information
  • Sources

About Huntington's disease

Huntington's disease usually develops between the ages of 30 and 50, but it can start at any age. Symptoms get worse gradually, sometimes over a period of up to 20 years. At the moment, there is no cure for the disease, but there are ways to help manage the symptoms.

Symptoms

The symptoms of Huntington's disease are sometimes overlooked. This is because they are mild at first and people without the disease can have the same symptoms. People who have Huntington's disease sometimes have problems for a long time before they find out that they have the condition.

Early symptoms include:

  • mild tremor
  • clumsiness
  • lack of concentration and irritability
  • difficulty remembering things
  • mood changes, including depression
  • aggressive antisocial behaviour

Over time the symptoms become progressively worse. Eventually, full-time nursing care will be needed. Later symptoms fall into three categories:

Physical symptoms

Physical symptoms include chorea (involuntary movements of the limbs, face and body). Chorea may lead to difficulty walking, speaking and swallowing. People often lose weight because of difficulty eating and by burning more calories due to the continuous movement. The ability to coordinate movement gets gradually worse as the disease progresses.

Emotional symptoms

Emotional symptoms include depression, not only because of the burden of having a progressive disorder, but as a direct result of the damage to certain brain cells. You may become frustrated at being unable to work or do previously simple tasks. You may behave stubbornly, and have mood swings. People with Huntington's may also become more irritable and antisocial than usual, or have less inhibitions.

Cognitive symptoms

Cognitive symptoms include a loss of drive and initiative. People with Huntington's may appear to be lazy or uninterested in life, spending days doing little or neglecting personal hygiene. You may also lose the ability to organise yourself. This is because planning skills and the ability to do more than one task at once deteriorate. In the later stages, you may get memory loss and be less able to understand speech.

The behavioural changes that occur are often the most distressing for you, your family and your carers. A previously full and active life may be lost with a gradual reduction in independence and mobility. At the same time, your personality can become gradually more self-centred and unmotivated, straining personal relationships.

Causes

Huntington's disease is caused by a faulty gene that runs in families. The gene, which was discovered in 1993, produces a protein called Huntingtin. Scientists are still researching how the faulty gene causes the disease.

Most genes in the body are present in two copies: one from your mother and one from your father. The gene that causes Huntington's disease is dominant. This means that if you inherit a copy of this gene from either parent, you will go on to develop the disease at some point in your life.

If you have one parent with Huntington's disease you have a 50 percent chance of inheriting the faulty gene. The risk is 50 percent for each child. It isn't altered by gender or whether brothers and sisters are affected. Only people who have the faulty gene can pass it on to their children.

Occasionally there is no family history of the condition. This may be because previous generations weren't diagnosed - either because of early death from other causes, or loss of contact through adoption.

Huntington's disease causes progressive damage to cells in areas of your brain called the basal ganglia and cerebral cortex. These areas are involved in the control of movement, planning, motivation and personality.

Juvenile Huntington's disease

A juvenile form of Huntington's disease, which develops before the age of 20, also exists. About five percent of people with Huntington's disease are affected by the condition when this young. The symptoms are similar to those of adult Huntington's, but muscular rigidity is more likely to occur. Epilepsy - which causes fits - is also more common among those with juvenile Huntington's disease compared with adults who have the condition.

Treatment

Although there is currently no cure for Huntington's disease, there are drugs to help manage some of your symptoms. There are medicines that can reduce the involuntary movements, and antidepressant medicines may alleviate depression. Mood stabilisers and antipsychotic drugs can help with some of the emotional disturbances.

Counselling can also be helpful, both for you and your family. Dieticians can advise on adequate calorie and nutrient intake to stop weight loss.

Future promise

Scientists are investigating several drug treatments to slow the progress of Huntington's disease. Some of these have shown promise and are planned to be tested in clinical trials. Examples include the antibiotic minocycline and coenzyme Q10. However, this research is speculative; more work is needed before any recommendations can be made.

Some clinical studies have used stem cells (the most basic form of cells from which others develop) to grow cells that can be transplanted into the brain of people affected by the disease. This approach may eventually improve the outlook for people with Huntington's disease. However, this research is still in the very early stages of development.

Genetic tests

There are tests available to find out whether you have the faulty gene. They fall into three categories: diagnostic, pre-symptomatic and antenatal.

Diagnostic tests

These are carried out if you have symptoms of Huntington's disease and you come from a family where others have the condition. The aim is to confirm the diagnosis.

Pre-symptomatic tests

These tests are carried out if you have no symptoms of Huntington's disease, but you have family members who are affected by it. The test tells you whether you will develop the disease, but not when it will happen.

The decision to take these tests is a serious one and shouldn't be rushed into. A positive result can be devastating since it may tell you that one day you will become severely ill. There are also issues surrounding testing when your parents have themselves not been tested. This is because a positive result means that one of your parents also has the faulty gene.

You should take advice from a genetic counsellor about the implications of taking the test before you go ahead. In the UK you can't have the test if you are under the age of 18.

Antenatal tests

These tests may be carried out early in pregnancy on the unborn children of couples from families affected by Huntington's disease. They can be used to calculate the risk of that child going on to develop the disease in their adult life.


Pre-implantation Genetic Diagnosis (PGD)

If you know that you carry the gene for Huntington's disease, you can opt for PGD. This is a type of in vitro fertilisation (IVF). Only embryos which are not carrying the faulty Huntington gene are used, so the baby is not at risk of having the disease.

Further information

Huntington's Disease Association

020 7022 1950

www.hda.org.uk

Scottish Huntington's Association

01505 322245

www.hdscotland.org

Sources

  • Walker FO. Huntington's disease. Lancet, 2007; 369: 218-228
  • HAD factsheets. Huntington's Disease Association. www.hda.org.uk, accessed 6 March 2007