Huntington’s disease is an inherited disease of the brain, for which there is no cure.
The disease damages the nerve cells in the brain causing deterioration and gradual loss of function of areas of the brain. This affects movement, cognition (perception), awareness, thinking, judgement and behaviour.
Huntington’s disease was originally called Huntington’s chorea, after the Greek word for dancing, as the associated involuntary movements can look like jerky dancing.
Who is affected?
Both men and women with a family history of Huntington’s can inherit the disease and symptoms usually start to show in adulthood.There are approximately 6,000 people with the disease in the UK.
Twice as many people may have inherited the disease but have not yet developed symptoms. This group, who are unaware they carry the disease, may have had children and passed on the disease without realising.
Juvenile (children’s) Huntington’s disease develops before the age of 20 years. Only 5-10% of people with Huntington’s develop the condition at a very young age, and the pattern of features may be different.
Symptoms of Huntington’s disease
People can start to show the symptoms of Huntington’s disease at almost any age but most will develop problems between the ages of 35 and 55 years.
Generally, the disease progresses and worsens for around 10 to 20 years until the person eventually dies. Symptoms vary between people; there is no typical pattern.
Early symptoms such as personality changes, mood swings and bizarre behaviour are often overlooked at first and attributed to something else.
Some people with Huntington’s may seem to refuse to accept their illness or the seriousness of it.
Behavioural changes are often the first symptoms to appear in Huntington’s disease and can be the most distressing. These symptoms often include:
- a lack of emotions and not recognising the needs of others in the family,
- alternating periods of aggression, excitement, depression, apathy, antisocial behaviour and anger,
- difficulty concentrating on more than one task, which causes irritability,
- short-term memory lapses, and
- problems with orientation.
A person with Huntington’s may display a lack of drive, initiative and concentration that may make them appear lazy. This is not the case; it is just the way the disease affects their personality. Also, someone with Huntington’s may develop a lack of interest in hygiene and self-care.
Apart from depression, there is no psychiatric disorder specifically associated with Huntington’s, although a few people may develop problems such as obsessive compulsive disorder (OCD), mania and schizophrenia.
Huntington’s disease affects movement and early symptoms include slight, uncontrollable movements of the face and jerking, flicking or fidgety movements of the limbs and body. These move from one area of the body to another and can cause the person to lurch and stumble.
As the disease progresses, the uncontrollable movements are more frequent and extreme. This may alter over time so that movements become slow and muscles more rigid.
People with Huntington’s disease tend to lose weight despite having a good appetite. They can find eating tiring, frustrating and messy because the muscles in the mouth and the diaphragm muscles do not work properly, due to the loss of control.
Loss of coordination can lead to spilling or dropping food. Swallowing is a problem, so choking on food and drink, particularly thin drinks like water, can be a common problem. You may be referred to a dietitian or a speech and language therapist if swallowing is difficult. In some cases, a feeding tube can be inserted.
Communication and cognition (perception, awareness, thinking and judgement) are affected by Huntington’s disease.
People with Huntington’s often have difficulty putting thoughts into words and slur their speech. They can understand what is being said but may not be able to communicate that they understand or respond. Impaired breathing can make speech difficult.
People with Huntington’s disease can experience problems with sexual relationships, such as loss of interest or making inappropriate sexual demands.
Causes of Huntington’s disease
Huntington’s disease is caused by a faulty gene that is found on chromosome number four.
The normal copy of the gene produces a protein called huntingtin but the faulty gene is larger than normal and produces a larger form of huntingtin.
Some cells in the brain are very sensitive to the effects of the abnormal huntingtin, and this causes them to function poorly and eventually die. Exactly how this happens is still unclear.
Chance of inheriting the disease
A parent with the Huntington’s gene has one good copy of the gene and one faulty copy of the gene and their child will inherit one of these genes. Therefore, there is a 50:50 chance the child will get the faulty gene. If they do get the faulty gene, they will develop Huntington’s disease.
There is then a 50:50 chance that the child with Huntington’s disease will pass the faulty gene on to their future child.
This pattern of inheritance is called autosomal dominant.
In as many as 3% of cases, there is no family history of the disease. This could be due to adoption or because relatives with the disease died early from other causes, or it could be a new genetic mutation (a new error in a gene).
Diagnosing Huntington’s disease
If someone is showing symptoms of Huntington’s disease and it is known to run in the family, genetic testing can confirm the diagnosis.
Taking a genetic test
The children of someone with Huntington’s disease can to take a genetic test (after the age of 18) to see if they have inherited the disease. If they have inherited the faulty gene, they will develop Huntington’s but it is not possible to work out at what age.
You can ask your GP to arrange an appointment for you at a regional genetic clinic. You will have some counselling, then two blood samples are taken. Your DNA is extracted from the blood sample and analysed to see if you have inherited the faulty gene.
You may have to wait two to four weeks for the test results.
Tests in pregnancy
If a parent is already known to have the Huntington’s disease gene, then it is possible to do a test on the pregnancy at 11 weeks. This needs careful consideration and can be discussed with a genetic counselling team.
Preimplantation genetic diagnosis
If one partner of a coupleis at risk of Huntington’s disease but does not want to find out if they have the disease, and the couple would like to have children free of risk, then more complex genetic testing is needed. One option is preimplantation genetic diagnosis.
Preimplantation genetic diagnosis involves having in-vitro fertilisation (IVF) treatment (see Useful links), and then genetically testing the embryo in a laboratory to see if it has the faulty gene. The embryo will only be placed inside the woman if it does not have the faulty gene.
The procedure is also an option for couples where one partner is known to have Huntington’s disease.
Preimplantation genetic diagnosis is not a straightforward procedure and it raises a number of issues that need to be considered in detail.
Treating Huntington’s disease
There is no cure for Huntington’s disease and its progress cannot be reversed or slowed down.
Medication can be used to manage some of the associated symptoms, and therapies (such as speech and language therapy and occupational therapy) can help with communication and day-to-day living.
Medication for Huntington’s disease
Medicines, which can be taken in liquid form if necessary, include:
- Antidepressants. These should be considered as they can improve mood swings and treat depression. They include:
– SSRI antidepressants such as fluoxetine, sertraline, citalopram and paroxetine,
– tricyclic antidepressants such as nortriptyline, and
– other types of antidepressants, including nefazodone, bupropion and venlafaxine.
- Medication to supress chorea (involuntary movements). These drugs include:
– tetrabenazine, which reduces the amount of dopamine (a chemical) reaching some of the nerve cells in the brain,
– benzodiazepines, such asclonazepam and diazepam,and
– neuroleptics, such as olanzapine, risperidone, quetiapine and haloperidol.
- Antipsychotic medication, such as fluphenazine, haloperidol, risperidone, olanzapine and quetiapine.
- Medication to treat mania (an abnormally high state of mood), such as neuroleptics (see above), sodium valproate and carbamazepine.