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

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.

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.

Early-onset form of Huntington disease is less common 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.

• Abnormal and unusual movements
  • Head turning to shift eye position
  • Facial movements, including grimaces
  • Slow, uncontrolled movements
  • Quick, sudden, jerking movements of arms, legs, face, and other body parts
  • Unsteady gait
• Behavior changes
  • Antisocial behaviors
  • Hallucinations
  • Irritability
  • Moodiness
  • Restlessness or fidgeting
  • Paranoia
  • Psychosis
• 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

In children:

• Rigidity
• Slow movements
• Tremor

The doctor will perform a physical exam. The doctor may see signs of dementia and abnormal movements. Reflexes may be abnormal. The gait is often "prancing" and wide. Speech may be hesitant or enunciation poor.

A head CT scan may 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 if you carry the gene for Huntington's disease.