In short
Huntington's disease is a genetic condition that causes brain cells to gradually break down and die, leading to uncontrollable movements, changes in thinking, and shifts in mood and behavior. It is passed down through families, and symptoms typically begin between the ages of 30 and 50, slowly worsening over time. While there is currently no cure, treatments and support can help manage symptoms and maintain quality of life for as long as possible.
Key points
- Huntington's disease is a genetic condition caused by an error in the huntingtin gene that leads to progressive brain cell death.
- If one of your parents has Huntington's disease, you have a 50% chance of inheriting the altered gene and developing the condition.
- Symptoms typically begin between ages 30 and 50, but can appear earlier or later depending on the number of CAG repeats in the gene.
- The disease affects movement, thinking, and emotions—causing chorea, memory problems, and mood changes that worsen over time.
- There is no cure for Huntington's disease, but treatments can help manage symptoms and improve quality of life.
- Genetic testing is available to determine if you carry the gene, but the decision to be tested is personal and should involve genetic counseling.
- A groundbreaking 2025 gene therapy trial showed a 75% slowing of disease progression, offering new hope for people affected by Huntington's disease.
- Living with Huntington's disease requires support from a team of healthcare professionals, including neurologists, therapists, counselors, and caregivers.
What Is Huntington's Disease?
Huntington's disease is an inherited disorder that attacks nerve cells in the brain, particularly in areas that control voluntary movement and memory. The disease is caused by a genetic mistake in a gene called huntingtin, which sits on chromosome 4. This genetic error involves a repeating pattern of three chemical letters (CAG) that appear too many times in the DNA. When these repeats are too long, the protein made by this gene becomes abnormally shaped and damages brain cells instead of helping them function properly.
The disease affects the whole brain, but certain areas are more vulnerable than others. The striatum, a region deep inside the brain that plays a key role in controlling movement, mood, and behavior, is the part most affected by Huntington's disease. Over time, the damage spreads to other regions, including the outer surface of the brain (the cortex), which regulates thinking, decision-making, and memory. This widespread destruction of nerve cells explains why Huntington's disease causes such a wide range of physical, mental, and emotional symptoms.
Huntington's disease is not just a movement disorder. While many people associate it with the dance-like, jerking movements called chorea, the disease also deeply affects a person's ability to think clearly, remember information, and regulate emotions. In fact, some people first notice behavioral or mood changes before any physical symptoms appear. This makes Huntington's disease a complex condition that requires comprehensive care and support from multiple healthcare professionals.
How Common Is Huntington's Disease?
Huntington's disease is considered a rare condition. It affects an estimated 3 to 7 out of every 100,000 people worldwide. The disease is most common in people of European ancestry, meaning those whose biological families come from European backgrounds. However, Huntington's disease can affect people of any ethnic or racial background.
There are two main types of Huntington's disease based on when symptoms first appear. Adult-onset Huntington's disease is by far the most common form, with symptoms typically beginning after age 30. Early-onset Huntington's disease, also called juvenile Huntington's disease, affects children and teenagers and is very rare. When Huntington's disease develops before age 20, it often presents with different symptoms and may progress more quickly than the adult form.
Causes and Genetics of Huntington's Disease
Huntington's disease is caused by a genetic change, or mutation, in the HTT gene. This gene provides instructions for making a protein called huntingtin, which helps nerve cells function properly. In people with Huntington's disease, the HTT gene contains an abnormal section where the sequence CAG is repeated too many times. In healthy people, this CAG sequence repeats fewer than 36 times. In people with Huntington's disease, it repeats 36 times or more.
The more times the CAG sequence repeats, the earlier symptoms tend to appear. When there are a very large number of repeats, the disease can begin in childhood or adolescence. This expanded CAG repeat causes the huntingtin protein to be made in an abnormally long form, with too many copies of the amino acid glutamine attached to it. This abnormal protein becomes misshapen and tends to clump together inside cells. These clumps interfere with normal cell function and eventually kill brain cells, particularly in the striatum and other regions involved in movement and thinking.
Huntington's disease is inherited in what is called an autosomal dominant pattern. This means that if one of your biological parents carries the altered gene, you have a 50% chance of inheriting it. If you inherit the gene, you will eventually develop Huntington's disease, although the age when symptoms begin can vary. In rare cases, the genetic change happens spontaneously without any family history of the condition, though this is uncommon.
Risk Factors for Huntington's Disease
The primary risk factor for Huntington's disease is having a biological parent who carries the altered HTT gene. Because the disease follows an autosomal dominant inheritance pattern, the risk is significant—50% for each child of an affected parent. The disease does not skip generations. If you inherit the gene, you will develop the disease at some point in your life, although the timing of symptom onset can vary widely.
The number of CAG repeats in the gene influences when symptoms will appear. People with a higher number of repeats tend to develop symptoms earlier in life. In some cases, the number of repeats can increase when the gene is passed from parent to child, a phenomenon called genetic anticipation. This is particularly common when the gene is inherited from the father, and it explains why some families see the disease appearing at younger ages in successive generations.
Anyone can develop Huntington's disease if they inherit the altered gene, but the disease is most commonly seen in people of European descent. There are no known lifestyle factors, environmental exposures, or behaviors that increase or decrease the risk of developing Huntington's disease in someone who carries the gene. The disease is purely genetic, and carrying the altered gene is both necessary and sufficient to eventually develop the condition.
Symptoms of Huntington's Disease
Huntington's disease causes a wide range of symptoms that affect movement, thinking, and emotions. The disease progresses slowly, meaning symptoms typically start out mild and gradually become more severe over many years. The first symptoms that appear can vary greatly from one person to another. Some people first notice small physical changes, while others experience mood shifts or difficulty with memory and thinking before any movement problems develop.
Physical and Movement Symptoms
The most recognizable physical symptom of Huntington's disease is chorea, which refers to involuntary, jerky, dance-like movements. Chorea often starts in the fingers, hands, feet, or face, with small twitching or fidgeting movements. Over time, these movements become more pronounced and spread to the arms, legs, and torso. Chorea can intensify when a person is nervous, distracted, or stressed. While chorea is common, not everyone with Huntington's disease experiences these movements. Some people become stiff and rigid instead, a condition called akinesia, where they move very little or not at all.
Other movement-related symptoms include loss of coordination, trouble walking, and difficulty with balance, which can increase the risk of falls. People with Huntington's disease may also develop unusual fixed postures, known as dystonia. Some people experience tremors, or unintentional back-and-forth muscle movements. Unusual eye movements can appear early in the disease and make it harder to track moving objects or shift gaze smoothly.
As the disease progresses, physical symptoms worsen and begin to interfere with daily activities. Speaking becomes slurred, and swallowing becomes difficult, which can lead to choking, weight loss, and an increased risk of lung infections. Walking becomes more challenging, and eventually, people with Huntington's disease may need mobility aids like walkers or wheelchairs. In the later stages, individuals become unable to care for themselves and require full-time assistance.
Cognitive and Thinking Symptoms
Huntington's disease affects the brain's ability to process information, learn new things, and make decisions. People with the disease often experience problems with attention, memory, and the ability to focus on more than one task at a time. They may have trouble organizing their thoughts, solving problems, or understanding complex instructions. Learning new information becomes more difficult, and it can take longer to process questions or respond in conversation.
Judgment and reasoning are also affected. People may have difficulty prioritizing tasks, deciding which things are most important, or planning ahead. Driving can become dangerous as reaction times slow and decision-making becomes impaired. Over time, these cognitive changes worsen and begin to significantly interfere with work, managing finances, keeping appointments, and handling household responsibilities.
Emotional and Behavioral Symptoms
Changes in mood and behavior are common in Huntington's disease and can be some of the earliest signs of the condition. People may become more irritable, impulsive, or prone to mood swings. They may lose interest in activities they once enjoyed, a symptom called apathy, which can be mistaken for laziness or depression. Depression, anxiety, and feelings of sadness are also very common and can significantly affect quality of life.
Some individuals develop more severe psychiatric symptoms, such as obsessive thoughts, compulsive behaviors, or paranoia. Behavioral changes may include becoming socially withdrawn, acting impulsively without thinking through consequences, or having trouble controlling anger. Family members and caregivers often notice these personality and behavioral changes before the person with Huntington's disease is aware of them.
Prevention of Huntington's Disease
Because Huntington's disease is caused by an inherited genetic mutation, there is currently no way to prevent the disease from developing in someone who carries the altered HTT gene. If you have the gene, you will eventually develop Huntington's disease, although when symptoms begin can vary. Research is ongoing to find treatments that could delay the onset of symptoms or slow the progression of the disease, but no preventive therapies are available yet.
For people at risk of inheriting Huntington's disease—meaning they have a parent with the condition—genetic testing is available. This test can determine whether you carry the altered gene before any symptoms appear. The decision to undergo genetic testing is deeply personal. Some people choose to be tested so they can plan for their future, make informed decisions about starting a family, or participate in research studies. Others prefer not to know their genetic status, especially since there is currently no cure or way to prevent the disease.
Genetic counseling is strongly recommended before and after genetic testing. A genetic counselor is a trained specialist who can help you understand what the test results mean, discuss the emotional and practical implications of knowing your genetic status, and provide support throughout the decision-making process. Genetic counseling services also extend to family planning. For individuals who carry the gene and wish to have children, options such as preimplantation genetic diagnosis (PGD) during in vitro fertilization (IVF) can help ensure that the altered gene is not passed to the next generation.
How Huntington's Disease Changes the Body
The underlying problem in Huntington's disease is the production of an abnormally shaped huntingtin protein due to the expanded CAG repeat in the HTT gene. This mutant protein is toxic to nerve cells. It tends to clump together inside cells, forming aggregates that interfere with normal cellular processes. These aggregates disrupt protein folding, damage cellular structures, and eventually lead to cell death.
The brain regions most affected are the striatum, which includes the caudate nucleus and the putamen, and the cerebral cortex. The striatum is responsible for controlling voluntary movements, regulating muscle tone, and influencing mood and behavior. As nerve cells in the striatum die, the brain loses its ability to coordinate smooth, purposeful movements, leading to chorea and other movement disorders. The death of neurons in the cortex affects higher-level thinking, memory, and emotional regulation.
At the molecular level, several processes contribute to cell damage in Huntington's disease. These include inflammation, oxidative stress (a kind of cellular wear and tear caused by harmful molecules called free radicals), and dysfunction of the mitochondria, the parts of cells that produce energy. The mutant huntingtin protein also disrupts communication between nerve cells by interfering with the balance of brain chemicals called neurotransmitters, particularly dopamine, glutamate, and gamma-aminobutyric acid (GABA). These chemical imbalances further contribute to the motor, cognitive, and psychiatric symptoms of the disease.
As the disease progresses, more and more neurons die, and the brain physically shrinks in size. This loss of brain tissue can be seen on imaging scans like MRI. The progressive death of nerve cells explains why symptoms steadily worsen over time and why Huntington's disease eventually affects nearly every aspect of a person's physical and mental functioning.
