Huntington disease

Huntington disease is a disorder in which nerve cells in certain parts of the brain waste away, or degenerate. The disease is passed down through families.

Causes

Huntington disease is caused by a genetic defect on chromosome 4. The defect causes a part of DNA to occur many more times than it is supposed to. This defect is called a CAG repeat. Normally, this section of DNA is repeated 10 to 28 times. But in persons with Huntington disease, it is repeated 36 to 120 times.

As the gene is passed down through families, the number of repeats tends to get larger. The larger the number of repeats, the higher a person's chance of developing symptoms at an earlier age. Therefore, as the disease is passed along in families, symptoms develop at younger and younger ages.

There are two forms of Huntington disease:

• Adult-onset is the most common. Persons with this form usually develop symptoms in their mid-30s or 40s.
• Early-onset affects a small number of people and begins in childhood or the teens.

If one of your parents has Huntington disease, you have a 50% chance of getting the gene. If you get the gene from your parents, you can pass it on to your children, who will also have a 50% chance of getting the gene. If you do not get the gene from your parents, you cannot pass the gene on to your children.

Symptoms

Behavior changes may occur before movement problems, and can include:

• Behavioral disturbances
• Hallucinations
• Irritability
• Moodiness
• Restlessness or fidgeting
• Paranoia
• Psychosis

Abnormal and unusual movements include:

• Facial movements, including grimaces
• Head turning to shift eye position
• Quick, sudden, sometimes wild jerking movements of the arms, legs, face, and other body parts
• Slow, uncontrolled movements
• Unsteady gait

Dementia that slowly gets worse, including:

• Disorientation or confusion
• Loss of judgment
• Loss of memory
• Personality changes
• Speech changes

Additional symptoms that may be associated with this disease:

• Anxiety, stress, and tension

  Anxiety, stress, and tension

  Stress is a feeling of emotional or physical tension. It can come from any event or thought that makes you feel frustrated, angry, or nervous. Stres...

   

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• Difficulty swallowing
• Speech impairment

Symptoms in children:

• Rigidity
• Slow movements
• Tremor

Exams and Tests

The doctor will perform a physical exam and may ask about the patient's family history and symptoms. An exam of the nervous system will also be done. The doctor may see signs of:

• Dementia
• Abnormal movements
• Abnormal reflexes
• "Prancing" and wide walk
• Hesitant speech or poor enunciation

Other tests that may show signs of Huntington disease include:

• Psychological testing
• Head CT or MRI scan

  CT

  A head computed tomography (CT) scan uses many x-rays to create pictures of the head, including the skull, brain, eye sockets, and sinuses.

   

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  MRI

  A head MRI (magnetic resonance imaging) is an imaging test that uses powerful magnets and radio waves to create pictures of the brain and surrounding...

   

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• PET (isotope) scan of the brain

  PET (isotope) scan of the brain

  A positron emission tomography scan is a type of imaging test. It uses a radioactive substance called a tracer to look for disease in the body. A po...

   

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Genetic testing is available to determine whether a person carries the gene for Huntington disease.

Treatment

There is no cure for Huntington disease. There is no known way to stop the disease from getting worse. The goal of treatment is to slow the symptoms and help the person function for as long as possible.

Medicines can be prescribed, depending on the symptoms.

• Dopamine blockers may help reduce abnormal behaviors and movements.
• Drugs such as amantadine and tetrabenazine are used to try to control extra movements.

Depression and suicide are common among persons with Huntington disease. It is important for caregivers to monitor for symptoms and seek medical help for the person right away.

As the disease progresses, the person will need assistance and supervision, and may eventually need 24-hour care.

Support Groups

Huntington's Disease Society of America -- hdsa.org

Outlook (Prognosis)

Huntington disease causes disability that gets worse over time. Persons with this disease usually die within 15 to 20 years. The cause of death is often infection. Suicide is also common.

It is important to realize that the disease affects everyone differently. The number of CAG repeats may determine the severity of symptoms. Persons with few repeats may have mild abnormal movements later in life and slow disease progression. Those with a large number of repeats may be severely affected at a young age.

When to Contact a Medical Professional

Call your health care provider if you or a family member develops symptoms of this disorder.

Prevention

Genetic counseling is advised if there is a family history of Huntington disease. Experts also recommend genetic counseling for couples with a family history of this disease who are considering having children.