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

Huntington chorea

American doctor George Huntington first described the disorder in 1872.

Huntington's disease is caused by a genetic defect on chromosome #4. The defect causes a part of DNA, called a CAG repeat, to occur many more times than it is supposed to. Normally, this section of DNA is repeated 10 to 35 times. But in persons with Huntington's disease, it is repeated 36 to 120 times.

As the gene is passed on from one generation to the next, the number of repeats - called a CAG repeat expansion - tend to get larger. The larger the number of repeats, the greater your chance of developing symptoms at an earlier age. Therefore, as the disease is passed along in families, it becomes evident at younger and younger ages.

There are two forms of Huntington's disease. The most common is adult-onset Huntington's disease. Persons with this form usually develop symptoms in their mid 30s and 40s.

An early-onset form of Huntington's disease accounts for a small number of cases and begins in childhood or adolescence. Symptoms may resemble those of Parkinson's disease with rigidity, slow movements, and tremor.

If one of your parents has Huntington's disease, you have a 50% chance of getting the gene for the disease. If you get the gene from your parents, you will develop the disease at some point in your life, and can pass it onto your children. If you do not get the gene from your parents, you cannot pass the gene onto your children.

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

• Antisocial behaviors
• Hallucinations
• Irritability
• Moodiness
• Restlessness or fidgeting
• Paranoia
• Psychosis

Abnormal and unusual movements include:

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

Dementia that slowly gets worse, including:

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

Additional symptoms that may be associated with this disease:

• Anxiety, stress, and tension
• Difficulty swallowing
• Speech impairment

Symptoms in children:

• Rigidity
• Slow movements
• Tremor

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

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

A head CT scanmay show loss of brain tissue, especially deep in the brain.

Other tests that may show signs of Huntington's disease include:

• Head MRI scan
• PET (isotope) scan of the brain

DNA marker studies may be available to determine whether you carry the gene for Huntington's disease.

There is no cure for Huntington's disease, and there is no known way to stop the disease from getting worse. The goal of treatment is to slow down the course of the disease and help the person function for as long and as comfortably as possible.

Medications vary depending on the symptoms. Dopamine blockers may help reduce abnormal behaviors and movements. Drugs such as haloperidol, tetrabenazine, and amantadine are used to try to control extra movements. There has been some evidence to suggest that co-enzyme Q10 may also help slow down the course of the disease.

Depression and suicide are common among persons with Huntington's disease. It is important for all those who care for a person with Huntington's disease to monitor for symptoms and treat accordingly.

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

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

Huntington's 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, although 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, while those with a large number of repeats may be severely affected at a young age.

• Loss of ability to care for self
• Loss of ability to interact
• Injury to self or others
• Increased risk of infection
• Depression
• Death

Call your health care provider if you develop symptoms of this disorder.

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

Lang A. Other movement disorders. In: Goldman L, Ausiello D, eds. Cecil Medicine. 23rd ed. Philadelphia, Pa: Saunders Elsevier;2007:chap 434.