What is Huntington's disease (HD)?
Huntington's disease (HD) is a genetic disease that’s passed from parent to child. It attacks the brain, causing unsteady and uncontrollable movements (chorea) in the hands, feet and face. Symptoms get worse over time. They eventually affect walking, talking and swallowing. It’s also common to have changes in emotion (feelings) and thinking, such as mood swings and memory problems.
Who does Huntington's disease (HD) affect?
Although anyone can develop HD, it tends to run in people of European descent (having family members who came from Europe). But the main factor is whether you have a parent with HD. If you do, you have a 50% chance of also having the disease.
What is juvenile Huntington’s disease (HD)?
Typically, HD symptoms appear in middle age. But with juvenile Huntington’s disease (JHD), symptoms begin in childhood. In addition to the symptoms of the adult disease, early signs in children may include seizures and stiffness. Children with JHD most often inherit the disease from their fathers.
How common is Huntington’s disease (HD)?
HD is rare, affecting about 30,000 Americans. In North America, the prevalence of HD was 5.7 per 100,000 people. Juvenile Huntington’s disease is even less common — children make up 5% to 10% of HD cases.
How is Huntington's disease (HD) inherited?
To understand how HD is inherited, you have to know a little bit about genetics — the study of physical characteristics passed down from generation to generation.
Every cell in your body has DNA (deoxyribonucleic acid). DNA is your body’s instruction manual. It provides the information you need to repair and rebuild cells. Your DNA dictates everything from your hair color and height to how your organs function.
Genes are like “chapters” within the DNA instruction manual. Here’s how genes affect Huntington’s disease:
- The huntingtin gene (HTT or HD gene) tells your body how to build the huntingtin protein. You get one HTT gene from each parent.
- If you have Huntington’s disease, one of your parents passed on an HTT gene with a mutation (like a misprint in a book). It tells your body to create an unusually long protein. Researchers believe this long protein damages and kills brain cells.
- Anyone who inherits the gene will eventually develop HD symptoms. The exact age when symptoms appear varies. Often, HD symptoms start earlier in each new generation than in the previous generation.
How does Huntington’s disease (HD) affect the brain?
Huntington’s disease develops when misshapen proteins destroy neurons (brain cells). First, they usually attack the basal ganglia, an area in the brain that oversees the body movements you control. The disease also impacts the brain’s cortex (surface of the brain). This part of the brain helps with thinking, decision-making and memory.
What are the symptoms of Huntington's disease (HD)?
HD affects a person both physically and mentally. Physical problems may start in small ways — for example, clumsiness or losing balance — and then get worse over time. If you have HD, you may develop:
- Uncontrolled movements (chorea).
- Emotional changes like mood swings, depression and irritability.
- Problems with memory, focus and multitasking.
- Slowed movements and speech.
- Slurred speech.
- Loss of hand coordination, such as being unable to hold a pencil.
- Difficulty swallowing.
What is Huntington’s disease chorea?
One of the first physical symptoms of HD is chorea, unintended jerks or twisting movements. Chorea usually affects hands, fingers and face muscles first. Later, it also makes your arms, legs and torso move uncontrollably. Chorea can make speaking, eating and walking more difficult. It may also affect your ability to perform everyday activities such as driving.
Can Huntington’s disease (HD) cause dementia?
In its later stages, HD can cause dementia. The loss of brain function leads to memory loss and personality changes.
Earlier in the disease, the impact on your brain is different. You might have problems multitasking or doing something that involves multiple steps. It could also be hard to plan or problem-solve soon after the onset of Huntington’s disease.