Huntington's disease

Some people have a sickness in their brain.

This sickness often comes from a parent. It can change how a person feels. It can also change how they move.

Their bodies might make jerky movements. These movements can look like a dance. It can also make it hard to talk. This sickness usually starts when people are older. Some children can get it too. Doctors help people feel better.

It is a very rare sickness.

Huntington's disease is a sickness that affects the brain.

It is usually passed down from a parent to a child. This happens because of a change in a gene. A gene is a tiny part of our body that holds instructions. In this disease, a part of the gene repeats too many times. This makes a broken protein. The broken protein damages brain cells over time. This damage often happens in a part of the brain called the basal ganglia.

The disease changes how a person moves and thinks. Many people get jerky movements called chorea. These movements can look like a dance. It can also make it hard to walk or talk. People may also feel sad or angry. These are called psychiatric symptoms. Most people see these signs around age 40. Some children get it too. This is called juvenile Huntington's disease. It can make the body feel stiff or slow. There is no cure yet. Doctors use medicine to help with some symptoms.

This chart shows how the disease moves through a family.

Huntington's disease is a serious brain condition. It is often called a neurodegenerative disease. This means it causes brain cells to break down over time.

The disease affects how a person moves and thinks. It also changes how they feel. Most people see these changes as they get older.

It is a very hard condition for families. Doctors are working hard to understand it better.

This disease works because of a change in a gene. Genes hold the instructions for our bodies. In this case, a tiny part of the gene repeats too many times. This is called a trinucleotide repeat expansion. These repeats happen in the huntingtin gene, or HTT. This change makes an abnormal protein. This mutant protein is toxic to brain cells. It slowly damages the basal ganglia. This is a part of the brain that helps control movement.

People first noticed this disease a long time ago. An American doctor named Charles Oscar Waters wrote about it in 1841. Later, in 1872, another doctor named George Huntington described it in more detail.

Scientists later found the cause of the disease. An international group led by the Hereditary Disease Foundation discovered the genetic cause in 1993. Since the late 1960s, groups have worked to help families. They want to teach people about the disease and find new treatments.

There are many important facts about how the disease appears. Symptoms usually start around age 40. However, they can start at any age. About 8% of cases are called juvenile Huntington's disease. This happens to people under age 20.

These younger people often have slow movements instead of jerky ones. The disease is also rare in places like Japan and Finland. It affects men and women the same amount. In some areas, it affects 4 to 15 people in every 100,000.

Understanding this disease helps us see how our bodies work. It shows how one tiny change in a gene can change everything. The jerky movements are called chorea. They can look like a dance. This happens because the brain cannot send the right signals to the muscles. This is similar to how a computer might glitch if its code is wrong. While there is no cure yet, medicine like tetrabenazine can help. This helps manage the movement problems for some people.

Huntington's disease (HD) is a fatal neurodegenerative condition. This means it causes the progressive breakdown of nerve cells in the brain. It is a complex disorder that affects three main areas: movement, thinking, and emotions.

These three areas are often called a triad of symptoms. Because it damages the brain over time, the symptoms get worse as the disease advances. It is a serious condition that requires full-time care in its later stages.

The disease is caused by a specific error in the huntingtin gene, known as HTT. This gene provides the instructions for making the huntingtin protein. Inside this gene, there is a section of DNA called a trinucleotide repeat. This section consists of a three-letter code, CAG, that repeats many times. In most people, this CAG sequence repeats a normal number of times. However, in people with HD, this section undergoes a trinucleotide repeat expansion. This means the CAG sequence repeats far more than it should.

This expansion leads to the production of a mutant huntingtin protein, or mHTT. This abnormal protein is toxic to brain cells. It causes damage through several possible biological mechanisms. One major effect is the degeneration of medium spiny neurons. These specific cells are located in the basal ganglia, a region of the brain that controls movement.

As these neurons die, the brain loses its ability to coordinate bodily functions.

Huntington's disease follows an autosomal dominant pattern of inheritance. This means a person only needs one copy of the mutated gene to develop the disease. If one parent has the mutation, each child has a 50% chance of inheriting it.

This probability is the same for both males and females. While most cases are inherited from a parent, up to 10% of cases result from a new mutation. This occurs when the mutation happens spontaneously without being passed down.

The symptoms of HD are often categorized into stages. In the early stages, people may experience subtle changes. These might include mood swings, irritability, or slight problems with thinking. These psychiatric symptoms can appear many years before physical movement problems. As the disease progresses into middle and late stages, the physical symptoms become much more obvious. One characteristic movement is chorea, which refers to involuntary, jerky, or "dance-like" body movements.

Another symptom is dystonia, which causes repetitive twisting or muscle rigidity.

Cognitive decline is also a major part of the disease. Patients often experience problems with executive functions. This includes difficulty planning, focusing on tasks, or controlling impulses. Memory deficits can also develop, affecting short-term, long-term, and working memory. Psychiatric symptoms can also include anxiety, depression, and even hallucinations. These mental health challenges are often the most distressing parts for families. Some people may also experience weight loss or difficulty swallowing.

History shows how much we have learned about this condition. The first description of the disease was recorded by Charles Oscar Waters in 1841. In 1872, George Huntington provided a much more detailed description of the symptoms.

It took much longer to find the cause. An international group led by the Hereditary Disease Foundation discovered the genetic basis in 1993. Today, researchers are studying stem-cell therapy to try and replace lost neurons. They are also testing new medications to slow the progression of the disease.

Statistics help us understand how common the disease is. HD affects about 4 to 15 people in every 100,000 of European descent. It is much rarer among Japanese and Finnish populations. Most people begin showing symptoms around age 40. However, about 8% of cases are known as juvenile HD, which starts before age 20.

In these younger cases, patients often show rigidity rather than chorea. Death usually occurs 15 to 20 years after the first symptoms appear. Common causes of death include heart disease or pneumonia.