Huntington's Disease

Overview

Huntington's disease is an inherited condition that causes nerve cells in the brain to gradually stop working properly and die. Affected brain areas include those that help control voluntary movement (movement done on purpose). People living with Huntington's disease develop uncontrollable movements, known as chorea, and abnormal body postures. The condition also causes problems with behavior, emotion, thinking, and personality.

There is no cure for Huntington's disease, but treatments help manage symptoms.

Related term: Huntington disease 

Signs and Symptoms

Early signs of Huntington's disease vary from person to person but often include mild clumsiness or problems with balance or movement and problems with mood, behavior, and thinking. Symptoms typically start in middle age, though in rare cases they appear in children. When they do, the disease is called juvenile Huntington's disease, and it usually gets worse quickly.

Movement symptoms include:

• Uncontrolled movements called chorea happen in the fingers, feet, face, or trunk that often get worse when a person is anxious or distracted and become more severe over time
• Problems with walking, which increases the likelihood of falls
• Rigidity (akinesia), which means moving very little or not at all, may happen in some people with Huntington's disease who do not develop chorea; Rigidity can also happen in later stages of the disease
• Unusual, fixed postures, called dystonia that can happen along with rigidity
• Tremors (unintentional rhythmic back-and-forth muscle movements)
• Abnormal eye movements, which often occur early in the disease
• Slurred speech
• Problems with eating, swallowing, and frequent choking
• Weight loss
• Lung infections (from trouble swallowing)
• Trouble sleeping, loss of energy, fatigue, and seizures

As Huntington's disease gets worse, people with the condition are no longer able to work, drive, or care for themselves.

Cognitive symptoms include:

• Trouble with driving, prioritizing tasks, and organizing
• Difficulty learning new things, remembering facts, putting thoughts into words, or answering questions
• Problems with judgment, attention, and decision-making
• Thinking and memory problems that can get worse over time and lead to dementia
  • Many people with Huntington's disease remain aware of their environment and can still express emotions

Behavioral symptoms include:

• Mood swings, irritability, lack of motivation, inactivity, depression, or anger
• Some people with Huntington's disease may have hostile outbursts, thoughts of suicide, deep depression, and losing touch with reality
• Withdrawal from social activities

Juvenile Huntington's disease symptoms may include:

• Rapid decline in school performance
• Myoclonus (rapid unwanted muscle twitches or jerks)
• Slowness
• Rigidity (muscles remaining constantly tense)
• Tremors
• Seizures
• Thinking and memory problems

Causes and Risk Factors

The Huntington's disease gene variant makes a protein called Huntingtin. The variant makes an incorrect form of this protein that is prone to clumping and eventually cell death. The basal ganglia and cortex are two brain areas affected in Huntington's disease. Together, they control coordinating movement, thought, perception, and memory.

The gene variant that causes Huntington's disease is present from birth. Because the inheritance pattern of Huntington's disease is dominant, a child needs only one abnormal copy of the gene from either parent to develop the disease. Since every gene from a parent has a 50% chance of being inherited by a child, each child of a parent with Huntington's disease has a 50% chance of inheriting the disease. If a child does not inherit the variant, they will not develop the disease and cannot pass it on to future generations.

Prevention Guidance

Genetic counselors can help people at risk make informed decisions about genetic testing, family planning, and prenatal testing for genetic disorders like Huntington's disease. Prenatal testing (testing before birth) can show whether a child will inherit the Huntington's disease variant, allowing parents to make informed decisions.

Diagnosis

A diagnosis of Huntington's disease is generally based on the results of neurological, psychological, and genetic testing.

Neurologic Exam and Medical History

To diagnose Huntington's disease, a neurologist conducts an in-depth interview to obtain a medical and family history and check for other conditions. Huntington's disease is almost always inherited, but in rare cases when it’s not, the condition is called sporadic Huntington's disease. Neurological and physical testing checks for reflexes, balance, movement, muscle tone, hearing, walking, and mental status. People with Huntington's disease may also be referred to specialists such as psychiatrists, genetic counselors, clinical neuropsychologists, and speech pathologists.

Genetic Testing

Central to diagnosing Huntington's disease is laboratory testing to identify the mutated gene (gene variant) present in Huntington's disease from a blood sample. This gene variant results in many DNA “words” (C-A-G, for cytosine-adenine-guanine) being repeated over and over. Most people have fewer than 27 CAG repeats in their Huntington's disease gene, so they are not at risk for the disease. People who have 27-35 CAG repeats are not likely to develop the disease, but they could still pass it on to future generations because the CAG repeat tends to increase in size from one generation to the next. People with Huntington's disease have 36 or more CAG repeats. Other variants within the CAG repeats can also affect the age of onset

Deciding to be tested for Huntington's disease can be difficult. Some people choose genetic testing to confirm a diagnosis when clear symptoms are present and there is a known family history of Huntington's disease. Others who have a parent with the disease decide to be tested to better understand their future, such as when planning to have children. A negative test relieves anxiety and uncertainty; a positive test enables people to make decisions about careers, marriage, and families. Some people at risk for Huntington's disease choose not to be tested, preferring to live with uncertainty rather than face the emotional consequences of a positive result or possible losses of insurance and employment. Genetic counselors can help people make these difficult decisions.

Diagnostic Imaging

In some cases, especially if a person’s family history and genetic testing are unclear, a doctor may recommend brain scans such as computed tomography (CT) or, more likely, magnetic resonance imaging (MRI). As Huntington's disease gets worse, brain scans may show that some brain areas shrink and fluid-filled spaces get larger. These changes Huntington's disease can occur in other brain disorders, and a person can have early symptoms of Huntington's disease and still have normal results from a CT or MRI scan.

Treatment and Management

There is no treatment that can stop or reverse Huntington's disease, but some symptoms can be treated. Most medicines that treat Huntington's disease symptoms work by affecting brain chemicals that help nerve cells communicate.

Medicines for movement symptoms include:

• Tetrabenazine, deutetrabenazine, and valbenazine, which treat chorea associated with Huntington's disease
• Antipsychotic drugs such as risperidone, olanzapine, or haloperidol, or other drugs such as clonazepam, which may help lessen chorea and control seeing things that aren’t there (hallucinations), having false beliefs (delusions) and experiencing violent outbursts

Medicines for emotional and behavioral symptoms include:

• Citalopram, fluoxetine, sertraline, nortriptyline, or other medicines that treat depression and anxiety
• Lithium to control extreme agitation and severe mood swings

Important notes about medicines:

• Some antipsychotic medicines can have side effects that worsen muscle contraction symptoms of Huntington's disease. People using these drugs should be closely monitored by their doctor or healthcare provider.
• Side effects of drugs used to treat Huntington's disease symptoms may include feeling tired or falling asleep, decreased ability to concentrate, restlessness, or becoming overstimulated.
• These drugs should be used only when symptoms create problems for the person living with Huntington's disease.

Find Clinical Trials

Clinical trials uncover better ways to prevent, diagnose, treat, and understand diseases and conditions. To ensure results apply to everyone, volunteers of all ages, sexes, and backgrounds, including both healthy individuals and those with specific medical conditions, are needed. Find clinical trials on Huntington's Disease.

Community Support

The following organizations provide support and information for people living with Huntington's disease and their families:

• Huntington’s Disease Society of America
• Hereditary Disease Foundation
• Huntington disease Buzz
• The Huntington disease Lighthouse
• National Library of Medicine

Additional information on Huntington's disease is available from:

• Hereditary Disease Foundation
• Huntington’s Disease Society of America

Note: This resource list is for informational purposes only. It is not comprehensive, and an organization’s inclusion does not constitute an endorsement by NIH.  

Research Information

The National Institutes of Health (NIH) is the largest public funder of biomedical research in the world. NIH invests most of its budget in medical research seeking to enhance life and to reduce illness and disability. NIH-funded research has led to breakthroughs and new treatments helping people live longer, healthier lives, and building the research foundation that drives discovery.

NIH-funded research has played a key role in understanding Huntington's disease, helping to localize the Huntington's disease-causing gene variant to chromosome 4 and identifying the variant that causes Huntington's disease.

Researchers are focusing on discovering and studying factors that hasten or delay disease onset, which would provide clues for strategies to slow or stop progression before symptoms even begin.

• Understanding Huntington's disease mechanisms: NIH-funded researchers are studying how the Huntingtin protein affects communication in and between brain cells as well as how its misshapen form contributes to disease.
• Biomarkers: NIH-funded researchers are looking for biomarkers for Huntington’s disease to find measurable biological indicators that can be used to predict, diagnose, or monitor a disease.
• Stem cells: NIH-funded researchers are using special laboratory-made cells, called induced pluripotent stem (iPS) cells, created from a person’s skin or blood to study Huntington's disease. These cells can be converted into brain cells to understand what goes wrong and to test new treatments for the condition. Researchers are exploring ways to use stem cells in the body to help repair damaged tissue. Huntington's disease. Another approach may be to mobilize stem cells already present in the body that can move into damaged tissue.
• Gene editing: Several groups of scientists are developing ways to change or inactivate the mutated gene to block production of the harmful version of the Huntingtin protein in cells or animals.
• Imaging: Researchers are using imaging technology to learn how Huntington's disease changes the brain’s structure, chemical activity, and function over time.
• Testing new medicines: Potential new medicines being tested include those designed to control or delay symptoms, and/or slow the rate of Huntington's disease progression. Others may protect overstimulated brain cells or target underlying causes of Huntington's disease.
• Environmental factors: NIH funds researchers who study how pesticides, pollution, and other contaminants in the environment may affect the brain, including their potential link to Huntington's disease.

Find NIH-funded research projects using NIH RePORTER, a searchable database of current and past research projects supported by NIH and other federal agencies.