Huntington's Disease (Huntington's Chorea)
Huntington’s disease is an inherited disorder that causes progressive symptoms and results from a faulty gene. This condition contributes to damaged nerve cells that cause problems with movement, coordination, cognition and behaviour.
In the past, Huntington’s disease was also known as Huntington’s chorea, which is taken from the Greek word meaning ‘to dance’. This relates to the movements, which are usually jerky and sudden in nature, caused by nerve damage. The term is no longer used because the symptoms of Huntington’s disease are much more diverse than jerky movements.
What exactly is Huntington’s disease?
Huntington’s disease is an inherited condition, which means that it is passed down from parents to their children. In most cases, symptoms develop after the age of 35. However, it is possible for signs to present at any stage of life. When symptoms develop before the age of 20, this is known as juvenile Huntington’s disease and the condition tends to progress rapidly.
Huntington’s is a progressive disorder, which means that symptoms get worse with time as the nerve cells degenerate. The symptoms are varied and affect movement, behaviour and mental capacity.
Huntington’s disease is a fatal condition and most people only survive for around 10-15 years after diagnosis. This is variable and some may live for up to 25 years.
Sometimes, Huntington’s disease can be hard to diagnose because initial symptoms can be associated with other conditions or behavioural disorders.
What causes Huntington’s disease?
Huntington’s disease occurs as a result of an inherited defective gene. This condition runs in families and is associated with chromosome number 4. In cases of Huntington’s disease, the normal copy of the chromosome number 4 creates a protein called huntingtin, while the faulty chromosome produces an abnormal type of huntingtin. The presence of abnormal huntingtin troubles the nerve cells in the basal ganglia and the cortex, affecting their function and eventually causing degeneration and producing symptoms such as impaired and involuntary movement, changes in behaviour and reduced cognition.
How does inheritance work?
If a parent has Huntington’s disease, this means they have one normal copy of chromosome number 4 and one mutant chromosome. This condition is known as autosomal dominant, which means that only one copy is needed to cause the individual to develop the disease. There is therefore a 50% chance that the parent will pass on the mutant gene to their child and a 50% chance that the child will not inherit the disease. If a child does inherit the disease, they then have a 50% likelihood of passing it on to their own child. Even if a child has the faulty gene, it is likely that they will not develop symptoms of Huntington’s disease until they are much older, usually over 35.
There are rare cases of Huntington’s where the patient has no family history of the disease. However, this may be due to the fact that parents have died early as a result of having the disease or as a result of adoption when the medical history of the birth parents is unknown. In very rare circumstances, Huntington’s disease may be caused by the expansion of the gene.
What are the symptoms of Huntington’s disease?
Huntington’s disease affects people in different ways and there are various symptoms, including:
Behavioural changes and mental health
These are often the first signs to become apparent and can also be the most upsetting for the individual and the people around them. This disorder can cause the following symptoms:
- lack of concentration and focus
- loss of motivation and disinterest, which may make people come across as lazy or distant
- a lack of emotion and compassion for others
- mood swings and bouts of anger, frustration and anxiety
- increased risk of depression
- lack of self-esteem and feelings of worthlessness
- development of obsessive thinking or habits
- lack of interest in social activities and becoming isolated
- episodes of feeling very high, followed by feeling very low
Studies show that people with Huntington’s disease are more likely to develop depression and in extreme cases, this may result in suicidal thoughts. This is most common just after diagnosis and as symptoms progress and they start to become more dependent on other people.
Huntington’s disease can affect the ability to make voluntary movements as well as increasing the frequency of involuntary actions. Possible symptoms may include:
- jerky movements that often come on suddenly
- involuntary muscle contractions and twitching
- lack of balance and coordination
- stiffness in the muscles
- fidgeting and restlessness
- abnormal facial movements
- impaired speech
Cognitive changes and Huntington’s disease
As symptoms progress and nerve cells degenerate, cognitive function may be impaired and symptoms include:
- difficulty learning and retaining new information
- lack of focus and getting distracted easily
- struggling with organisation
- slow speech and difficulty processing the formation of sentences
- difficulty responding in a conversation - even when a person understands what is being said to them, they may struggle to formulate sentences in response and this makes communication difficult
Feeding and appetite with Huntington’s disease
People who have Huntington’s disease tend to experience difficulties with eating and maintaining their weight. Even those with a good appetite tend to lose weight and eating can become a chore rather than something that is enjoyable. As the muscles can be impaired, eating can also become messy and embarrassing and swallowing may become increasingly difficult, which increases the risk of choking.
Symptoms of juvenile Huntington’s disease
Juvenile Huntington’s disease affects people under the age of 20 and symptoms may differ. The most common symptoms include:
- a sudden downward turn in performance at school or college
- muscles twitches, stiffness in the muscles and restricted movement
- difficulty with fine motor skills, such as writing
- issues related to behaviour
How is Huntington’s disease diagnosed?
Going to your GP is usually the first port of call if you experience symptoms associated with Huntington’s disease, for example jerky movements, muscle stiffness and changes in behaviour. Your GP will ask you questions about your symptoms and chat to you about your general health. If they suspect Huntington’s disease may be a possibility, they will refer you for specialist tests and treatment. In many cases, as the symptoms can be general to begin with, a diagnosis is made some time after the initial symptoms become apparent.
If there is family history of Huntington’s disease and a patient has symptoms associated with the disorder, genetic testing can be used to confirm a diagnosis. The test is used to determine if there is a defective copy of chromosome number 4.
If you have a parent with Huntington’s disease, genetic testing is available for over 18’s. The results of the test show whether you have inherited the faulty gene and this can help you to plan for the future. It is important to note that the test can tell you whether or not you have the faulty gene, but it cannot tell you when you will develop symptoms. If the test result is positive, counselling and specialist help will be made available to you. The results of genetic testing are usually available within 2-4 weeks.
MRI and CT scans may be ordered to detect changes in the brain. Initially, there might be no obvious alterations, but as the disease progresses, changes will become more noticeable.
If you or your partner has Huntington’s disease, it is possible to undergo screening during pregnancy and a genetic test is available at 11-12 weeks. If a couple is unsure about whether to go ahead and try for a baby or worried about having a baby with the defective gene, a process called pre-implantation genetic diagnosis may be recommended. In this case, IVF is involved and the genetic test is carried out while the embryo is still in the laboratory. If the embryo tests negative, it will then be implanted into the womb and you will have peace of mind that there is no risk of the baby developing Huntington’s disease later in life.
Is it advisable to get tested for Huntington’s disease?
It can be difficult to make a decision about whether or not to get tested if you have family history of Huntington’s disease. Some people want to know whether they have the gene, while others would rather not find out. If you are thinking about genetic testing, it is often beneficial to talk a counsellor beforehand.
Possible complications of Huntington’s disease
Huntington’s disease is progressive and eventually results in death. Most people live for between 10 and 15 years, but this can vary significantly and some people may survive for up to 30 years. In cases of juvenile Huntington’s disease, progression is faster and most deaths occur within 10 years.
Although there is no cure for Huntington’s disease, treatments such as physiotherapy, speech therapy and counselling are beneficial. Speech and language, occupational therapy and help with diet and nutrition can also help to improve quality of life and encourage independence.
As the disease progresses, people become increasingly dependent and their risk of life-threatening infections and accidents increases. The most common causes of death include choking, complications with not being able to swallow properly, infections (most commonly pneumonia) and injuries caused by falls and other types of accident.
If you need more information about Huntington’s disease or you would like to talk to people dealing with the condition, it is advisable to contact the Huntington’s Disease Association.
Treatments for Huntington’s disease
There is no cure for Huntington’s disease, but treatments are available to tackle symptoms and make day to day life easier. Treatments and therapies include:
Medicines may be prescribed to boost mental and physical health. Types of medicine often recommended include:
- Anti-depressants, including SSRI’s and trycyclic medications - these medicines help to reduce the risk of depression. Examples include fluoxetine, citalopram and amitriptyline. Possible side-effects of anti-depressants include sweating, shakes, tremors, sleep disturbance and constipation.
- Medicines to stabilise mood and prevent mood swings, including carbamazepine, which is proven to reduce irritability
- Antipsychotic medications, such as olanzapine - possible side-effects of anti-psychotic medicines include drowsiness, stiffness and tremors.
- Medicines designed to stop involuntary muscle contraction, including tetrabenazine
Therapies such as speech and language and occupational therapy, physiotherapy and counselling can help to make practical tasks easier, improve movement and reduce the risk of anxiety and depression. Help with diet can also be beneficial, especially at the stage when swallowing becomes more difficult.