Causes

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 28 times. But in persons with Huntington's disease, it is repeated 36 to 120 times.

As the gene is passed down through families, the number of repeats 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, symptoms develop 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.

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.

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
• Difficulty swallowing
• Speech impairment

Symptoms in children:

• Rigidity
• Slow movements
• Tremor

Exams and Tests

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 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

Genetic tests are available to determine whether a person carries the gene for Huntington's disease.

Treatment

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 symptoms 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 amantadine and tetrabenazine 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, but it is not conclusive.

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

Support Groups

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

Outlook (Prognosis)

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.

Possible Complications

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

When to Contact a Medical Professional

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

Prevention

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.

Alternative Names

Huntington chorea

References

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

Jankovic J, Shannon KM. Movement disorders. In: Bradley WG, Daroff RB, Fenichel GM, Jankovic J, eds. Bradley: Neurology in Clinical Practice. 5th ed. Philadelphia, Pa: Butterworth-Heinemann Elsevier; 2008:chap 75.

Update Date: 4/30/2012

Reviewed by: Kevin Sheth, MD, Department of Neurology, University of Maryland School of Medicine, Baltimore, MD. Review provided by VeriMed Healthcare Network. Also reviewed by David C. Dugdale, III, MD, Professor of Medicine, Division of General Medicine, Department of Medicine, University of Washington School of Medicine;David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.