Huntington's disease (HD) is an inherited disorder that causes brain cells, called neurons, to die in various areas of the brain, including those that help to control voluntary (intentional) movement.
Symptoms of the disease, which gets progressively worse, include uncontrolled movements (called chorea), abnormal body postures, and changes in behavior, emotion, judgment, and cognition.
People with HD also develop impaired coordination, slurred speech, and difficulty feeding and swallowing.
HD typically begins between ages 30 and 50. An earlier onset form called juvenile HD occurs under age 20.
Its symptoms differ somewhat from adult onset HD and include rigidity, slowness, difficulty at school, rapid involuntary muscle jerks called myoclonus, and seizures. More than 30,000 Americans have HD.
Huntington’s disease is caused by a mutation in the gene for a protein called huntingtin. The defect causes the cytosine, adenine, and guanine (CAG) building blocks of DNA to repeat many more times than is normal.
Each child of a parent with HD has a 50-50 chance of inheriting the HD gene. A child who does not inherit the HD gene will not develop the disease and generally cannot pass it to subsequent generations. A person who inherits the HD gene will eventually develop the disease.
HD is generally diagnosed based on a genetic test, medical history, brain imaging, and neurological and laboratory tests.
There is no treatment that can stop or reverse the course of HD. Tetrabenazine and deuterabenazine can treat chorea associated with HD.
Antipsychotic drugs may ease chorea and help to control hallucinations, delusions, and violent outbursts. Drugs may be prescribed to treat depression and anxiety.
Side effects of drugs used to treat the symptoms of HD may include fatigue, sedation, decreased concentration, restlessness, or hyperexcitability, and should be only used when symptoms create problems for the individual.
Huntington’s disease causes disability that gets worse over time. Currently no treatment is available to slow, stop, or reverse the course of HD.
People with HD usually die within 10 to 30 years following symptom onset, most commonly from infections (most often pneumonia) and injuries related to falls.
A major focus of research on HD is to understand the toxicity of mutant huntingin protein to brain cells and to develop potential drugs for counteracting it.
The HD gene discovery, which NINDS-funded research helped to identify, is allowing scientists to recruit individuals who carry the HD gene into clinical studies before they become ill.
Researchers hope to understand how the defective gene affects various structures in the brain and the body's chemistry and metabolism.
Some of the clinical symptoms in neurodegenerative diseases may be caused by the ultimate malfunctioning of neuronal circuits.
Scientists are using cutting-edge methods such as optogenetics (where neurons are activated or silenced in the brains of living animals using light beams) to study such circuit defects in HD.
Scientists are also using stem cells to study disease mechanisms and test potential therapeutic drugs.