Overview
Huntington's disease is a rare, inherited disease that causes the progressive breakdown (degeneration) of nerve cells in the brain. Huntington's disease has a wide impact on a person's functional abilities and usually results in movement, thinking (cognitive) and psychiatric disorders.
Huntington's disease symptoms can develop at any time, but they often first appear when people are in their 30s or 40s. If the condition develops before age 20, it's called juvenile Huntington's disease. When Huntington's develops early, symptoms are somewhat different and the disease may progress faster.
Medications are available to help manage the symptoms of Huntington's disease. But treatments can't prevent the physical, mental and behavioral decline associated with the condition.
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Symptoms
Huntington's disease usually causes movement, cognitive and psychiatric disorders with a wide spectrum of signs and symptoms. Which symptoms appear first varies greatly from person to person. Some symptoms appear more dominant or have a greater effect on functional ability, but that can change throughout the course of the disease.
Movement disorders
The movement disorders related to Huntington's disease may cause movements that can't be controlled, called chorea. Chorea are involuntary movements affecting all the muscles of the body, specifically the arms and legs, the face and the tongue. They also can affect the ability to make voluntary movements. Symptoms may include:
- Involuntary jerking or writhing movements.
- Muscle rigidity or muscle contracture.
- Slow or unusual eye movements.
- Trouble walking or keeping posture and balance.
- Trouble with speech or swallowing.
People with Huntington's disease also may not be able to control voluntary movements. This can have a greater impact than the involuntary movements caused by the disease. Having trouble with voluntary movements can affect a person's ability to work, perform daily activities, communicate and remain independent.
Cognitive conditions
Huntington's disease often causes trouble with cognitive skills. These symptoms may include:
- Trouble organizing, prioritizing or focusing on tasks.
- Lack of flexibility or getting stuck on a thought, behavior or action, known as perseveration.
- Lack of impulse control that can result in outbursts, acting without thinking and sexual promiscuity.
- Lack of awareness of one's own behaviors and abilities.
- Slowness in processing thoughts or ''finding'' words.
- Trouble learning new information.
Mental health conditions
The most common mental health condition associated with Huntington's disease is depression. This isn't simply a reaction to receiving a diagnosis of Huntington's disease. Instead, depression appears to occur because of damage to the brain and changes in brain function. Symptoms may include:
- Irritability, sadness or apathy.
- Social withdrawal.
- Trouble sleeping.
- Fatigue and loss of energy.
- Thoughts of death, dying or suicide.
Other common mental health conditions include:
- Obsessive-compulsive disorder, a condition marked by intrusive thoughts that keep coming back and by behaviors repeated over and over.
- Mania, which can cause elevated mood, overactivity, impulsive behavior and inflated self-esteem.
- Bipolar disorder, a condition with alternating episodes of depression and mania.
Weight loss also is common in people with Huntington's disease, especially as the disease gets worse.
Symptoms of juvenile Huntington's disease
The start and progression of Huntington's disease in younger people may be slightly different from that in adults. Problems that often present early in the course of the disease include:
Behavioral changes
- Difficulty paying attention
- Rapid, significant drop in overall school performance
- Behavioral problems
Physical changes
- Contracted and rigid muscles that affect gait (especially in young children)
- Tremors or slight involuntary movements
- Frequent falls or clumsiness
- Seizures
When to see a doctor
See your healthcare professional if you notice changes in your movements, emotional state or mental ability. The symptoms of Huntington's disease also can be caused by a number of different conditions. Therefore, it's important to get a prompt and thorough diagnosis.
Causes
Autosomal dominant inheritance pattern
Autosomal dominant inheritance pattern
In an autosomal dominant disorder, the changed gene is a dominant gene. It's located on one of the nonsex chromosomes, called autosomes. Only one changed gene is needed to be affected by this type of condition. A person with an autosomal dominant condition — in this example, the father — has a 50 percent chance of having an affected child with one changed gene. The person has a 50 percent chance of having an unaffected child.
Huntington's disease is caused by an inherited difference in a single gene. Huntington's disease is an autosomal dominant disorder, which means that a person needs only one copy of the nontypical gene to develop the disorder.
With the exception of genes on the sex chromosomes, a person inherits two copies of every gene — one copy from each parent. A parent with a nontypical gene could pass along the nontypical copy of the gene or the healthy copy. Each child in the family, therefore, has a 50% chance of inheriting the gene that causes the genetic disorder.
Risk factors
People who have a parent with Huntington's disease are at risk of having the disease themselves. Children of a parent with Huntington's have a 50 percent chance of having the gene change that causes Huntington's.
Complications
After Huntington's disease starts, a person's functional abilities gradually worsen over time. The rate of disease progression and duration varies. The time from the first symptoms to death is often about 10 to 30 years. Juvenile Huntington's disease usually results in death within 10 years after symptoms develop.
The clinical depression associated with Huntington's disease may increase the risk of suicide. Some research suggests that the greatest risk of suicide occurs before a diagnosis is made and in the middle stages of the disease when a person starts to lose independence.
Eventually, a person with Huntington's disease requires help with all activities of daily living and care. Late in the disease, the person will likely be confined to a bed and unable to speak. Someone with Huntington's disease is generally able to understand language and has an awareness of family and friends, though some won't recognize family members.
Common causes of death include:
- Pneumonia or other infections
- Injuries related to falls
- Complications related to the inability to swallow
Prevention
People with a known family history of Huntington's disease are understandably concerned about whether they may pass the Huntington gene on to their children. These people may consider genetic testing and family planning options.
If an at-risk parent is considering genetic testing, it can be helpful to meet with a genetic counselor. A genetic counselor will discuss the potential risks of a positive test result, which would indicate that the parent will develop the disease. Also, couples will need to make additional choices about whether to have children or to consider alternatives, such as prenatal testing for the gene or in vitro fertilization with donor sperm or eggs.
Another option for couples is in vitro fertilization and preimplantation genetic diagnosis. In this process, eggs are removed from the ovaries and fertilized with the father's sperm in a laboratory. The embryos are tested for presence of the Huntington gene, and only those testing negative for the Huntington gene are implanted in the mother's uterus.
In vitro fertilization
In vitro fertilization
During in vitro fertilization, eggs are removed from sacs called follicles within an ovary (A). An egg is fertilized by injecting a single sperm into the egg or mixing the egg with sperm in a petri dish (B). The fertilized egg, called an embryo, is transferred into the uterus (C).