Inheriting Huntington’s Disease
Huntington’s disease is an inherited disease that causes the progressive breakdown of nerve cells in the brain. Huntington’s disease has a broad impact on a person’s functional abilities and usually results in movement, thinking and psychiatric disorders.
Most people with Huntington’s disease develop signs and symptoms in their 40s or 50s, but the onset of disease may be earlier or later in life. When disease onset begins before age 20, the condition is called juvenile Huntington’s disease. Earlier onset often results in a somewhat different presentation of symptoms and faster disease progression.
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.
Symptoms of Huntington’s Disease
Huntington’s disease usually causes movement, cognitive and psychiatric disorders with a wide spectrum of signs and symptoms. Which symptoms appear first varies greatly among affected people. During the course of the disease, some disorders appear to be more dominant or have a greater effect on functional ability.
Movement Disorders Associated with Huntington’s Disease
The movement disorders associated with Huntington’s disease can include both involuntary movements and impairments in voluntary movements:
- Involuntary jerking or writhing movements (chorea)
- Involuntary, sustained contracture of muscles (dystonia)
- Muscle rigidity
- Slow, uncoordinated fine movements
- Slow or abnormal eye movements
- Impaired gait, posture and balance
- Difficulty with the physical production of speech
- Difficulty swallowing
Impairments in voluntary movements — rather than the involuntary movements — may have a greater impact on a person’s ability to work, perform daily activities, communicate and remain independent.
Cognitive Disorders Associated with Huntington’s Disease
Cognitive impairments often associated with Huntington’s disease include:
- Difficulty planning, organizing and prioritizing tasks
- Inability to start a task or conversation
- Lack of flexibility, or the tendency to get stuck on a thought, behavior or action (perseveration)
- Lack of impulse control that can result in outbursts, acting without thinking and sexual promiscuity
- Problems with spatial perception that can result in falls, clumsiness or accidents
- Lack of awareness of one’s own behaviors and abilities
- Difficulty focusing on a task for long periods
- Slowness in processing thoughts or “finding” words
- Difficulty in learning new information
Psychiatric Disorders Associated with Huntington’s Disease
The most common psychiatric disorder 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 injury to the brain and subsequent changes in brain function. Signs and symptoms may include:
- Feelings of sadness or unhappiness
- Loss of interest in normal activities
- Social withdrawal
- Insomnia or excessive sleeping
- Fatigue, tiredness and loss of energy
- Feelings of worthlessness or guilt
- Indecisiveness, distractibility and decreased concentration
- Frequent thoughts of death, dying or suicide
- Changes in appetite
- Reduced sex drive
Other common psychiatric disorders include:
- Obsessive-compulsive disorder, a condition marked by recurrent, intrusive thoughts and repetitive behaviors
- Mania, which can cause elevated mood, overactivity, impulsive behavior and inflated self-esteem
- Bipolar disorder, or alternating episodes of depression and mania
Other changes in mood or personality, but not necessarily specific psychiatric disorders, may include:
- Sexual inhibition or inappropriate sexual behaviors
Symptoms of Juvenile Huntington’s Disease
The onset and progression of Huntington’s disease in younger people may be slightly different from that in adults. Problems that often present themselves early in the course of the disease include:
- Loss of previously learned academic or physical skills
- Rapid, significant drop in overall school performance
- Behavioral problems
- Contracted and rigid muscles that affect gait (especially in young children)
- Changes in fine motor skills that might be noticeable in skills such as handwriting
- Tremors or slight involuntary movements
Treatments for Huntington’s Disease
- Speech therapy
- Physical and occupational therapy
When to see a doctor
See your doctor if you notice changes in your movements, emotional state or mental ability. The signs and symptoms of Huntington’s disease can be caused by a number of different conditions. Therefore, it’s important to get a prompt, thorough diagnosis.
Huntington’s disease is caused by an inherited defect in a single gene. Huntington’s disease is an autosomal dominant disorder, which means that a person needs only one copy of the defective 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 defective gene could pass along the defective copy of the gene or the healthy copy. Each child in the family, therefore, has a 50 percent chance of inheriting the gene that causes the genetic disorder.
After the start of Huntington’s disease, a person’s functional abilities gradually worsen over time. The rate of disease progression and duration varies. The time from disease emergence 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 greater risk of suicide occurs before a diagnosis is made and in the middle stages of the disease when a person has begun to lose independence.
Eventually, a person with Huntington’s disease requires help with all activities of daily living and care. Late in the disease, he or she will likely be confined to a bed and unable to speak. However, he or she is generally able to understand language and has an awareness of family and friends.
Common causes of death include:
- Pneumonia or other infections
- Injuries related to falls
- Complications related to the inability to swallow
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 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.