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What is HD?

March 31, 2014

Huntington's Disease Youth Organization

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What is HD?

Huntington’s disease is a genetic disorder which is caused by an expanded gene in a person’s DNA. Everybody has the gene that causes Huntington’s disease, but people that develop the condition have a longer version of the gene. It is that expansion which causes the gene not to work properly and eventually causes people to develop the condition.

Huntington’s disease is also a ‘neurodegenerative disorder’. But what does neurodegenerative disorder actually mean?! Well, if you break it down, neuro means ‘nerve’ and degenerative means something that gradually gets worse. Disorder is another word for a condition, or disease. So when people say Huntington’s is a neurodegenerative disorder, they are saying that Huntington’s is a condition which affects the nervous system and gradually gets worse over time. This means the condition affects the cells of our brains and continues to cause damage as time progresses which stops the brain and body from working as well as they used to. As a result, people develop symptoms of Huntington’s disease. These symptoms can be divided into three main types: involuntary movements, cognitive and behavioural.

Main types of symptoms

School room

You may hear doctors or health care professionals use the word ‘Chorea’ when talking about Huntington’s disease. Chorea is actually a Greek word, which means ‘dance’, and it is used to refer to the irregular movements people with Huntington’s disease have. These movement symptoms often cause people with Huntington’s disease to fall or drop things a lot, look restless and appear ‘fidgety’. In the early to middle stages of the disease people can sometimes be mistaken for being drunk, when in fact they have movement symptoms. It is these movements that are probably the thing people notice most about Huntington’s disease, and before doctors understood more about the other symptoms (like those that affect the way we think), they used to call the condition Huntington’s Chorea.

Cognitive describes anything that requires ‘intellectual activity’ or our process of thinking, basically anything that you have to put some thought into (like reading this page)! As the disease progresses, people with Huntington’s disease may have difficulty keeping track of things, making decisions or answering questions - that’s because the ability to concentrate becomes more difficult for people with Huntington’s disease, as a result of their cognitive skills declining. However, despite the loss of thinking ability, people with Huntington’s disease usually remain able to understand and recognise others.

The condition can also affect people behaviourally, meaning that it affects the way people think and the actions they take. Behavioural symptoms can cause people with Huntington’s disease to feel depressed, anxious, lack energy, get angry easily or lose their temper over things that don’t seem important. Sometimes people with Huntington’s disease behave inappropriately and do or say things they don’t mean to (without thinking). These people are experiencing the behavioural symptoms of Huntington’s disease and it is important to remember that when someone with Huntington’s disease does something that upsets you or makes you mad - it is most likely the Huntington’s disease causing them to behave this way.

Everyone is different

Although Huntington’s disease can affect movements, cognitive function and cause behavioural symptoms, each person is impacted individually and it is impossible to predict how each person will be affected. For example, one person with Huntington’s disease may have severe involuntary movements (chorea), but very few behavioural symptoms. Another person with the condition may have a lot of behavioural symptoms but only slight movements. Even two people from the same family, who are both affected by Huntington’s disease, may have completely different symptoms of the same disease.


Mad scientist

Symptoms of Huntington’s disease can begin at any age; but most people with Huntington’s disease usually develop symptoms between 30 and 50 years of age. Huntington’s disease is caused by damage to the brain, particularly an area of the brain called the ‘basal ganglia’. The brain cells deteriorate over a long period of time, usually 15-20 years, and during this time the affected person slowly loses their abilities, such as walking, talking and eating. This happens gradually and the person with Huntington’s disease can remain reasonably well for some time - even after being diagnosed with symptoms.

The figures

Worldwide roughly one person in every eight thousand is affected by Huntington’s disease - so it is quite a rare disease. But some places have more cases of Huntington’s disease than others. For example, the condition is common in places like Europe or North America and it’s also extremely common in a certain area of Venezuela. But the condition is thought to be far less common in places such as Asia and Africa, although not enough research has been done on these two continents to know exactly how many people are affected there. Huntington’s is often referred to as a ‘family disease’ because of the affect it can have on the entire family and the fact the disease is hereditary - so the condition impacts on far more lives than the figures suggest.


There is no cure or effective treatment which will slow down the progression of Huntington’s disease yet. But there are treatments that can help control some of the symptoms and there is a lot of research being done at the moment so there is great hope for the future! Visit our research section to find out more about advances in research. We hope this website has helped understand Huntington’s disease - however it affects you.

Hopefully this introduction to HD has helped. For more detailed information on HD and how it impacts on young people, check out the rest of HDYO’s content.