Huntington’s disease
Huntington’s disease is a rare inherited disorder that causes the progressive breakdown (degeneration) of nerve cells in the brain. Huntington’s disease has a large impact on a person’s functional abilities and usually causes movement, thinking (cognitive), and psychiatric disorders.
Huntington’s disease is caused by changes (mutations) in the HTT gene and is inherited in an autosomal dominant fashion.
Signs and symptoms usually develop between the ages of 35 and 44 and can include uncontrolled movements, loss of brainpower, and various emotional and psychiatric problems. People with HD usually live for about 15-20 years after the condition starts. There is also a less common form of early-onset Huntington’s disease that begins in childhood or adolescence.
Cause
Huntington’s disease is caused by an inherited defect in a single gene. Huntington’s disease is an autosomal dominant disease, which means that a person only needs one copy of the faulty gene to develop the disease.
With the exception of genes on the sex chromosomes, a person inherits two copies of each gene, one copy from each parent. A parent with a defective gene could pass on the defective copy of the gene or the healthy copy. Therefore, each child in the family has a 50% chance of inheriting the gene that causes the genetic disease.
Symptoms
Symptoms usually begin between the ages of 30 and 50, but can start much earlier or later.
Symptoms of Huntington’s disease can include:
- difficulty concentrating and memory lapses
- depression
- insomnia
- drop in energy
- frequent thoughts of death or suicide
- balance problems and easily tripping while walking
- clumsiness
- involuntary jerks or restless movements of the limbs and body
- mood swings, personality changes, psychiatric disorders (mania, bipolar disorder, obsessive-compulsive disorder)
- problems swallowing, speaking and breathing
- difficulty moving
Eventually, a person with Huntington’s disease needs help with all activities of daily living and care. At the end of the illness, he will likely be bedridden and unable to speak. Someone with Huntington’s disease is usually able to understand speech and has awareness of family and friends, although some do not recognize family members.
Common causes of death include:
- Pneumonia or other infections
- Injuries related to falls
- Complications related to the inability to swallow
Frequency
If one parent has the Huntington’s disease gene, there is a:
- 1 in 2 (50%) chance that each of their children will develop the condition: Affected children are also able to pass the gene on to all children who have it
- 1 in 2 (50%) chance each of their children will never develop the condition: Unaffected children cannot pass the condition on to children who have it.
Very occasionally, it is possible to develop Huntington’s disease without having a family history of it. But that’s usually just because one of your parents was never diagnosed.
Treatments
There is currently no cure for Huntington’s disease or any way to stop it from getting worse. But treatment and support can help reduce some of the problems caused by the condition.
Research into new treatments is ongoing, and there have recently been some promising results.
Medications can help reduce some of the problems caused by Huntington’s disease, but they don’t stop or slow the condition.
These include:
- antidepressants for depression
- medicines to relieve mood swings and irritability
- medicines to reduce involuntary movements
Prevention
People with a known family history of Huntington’s disease are understandably concerned about whether they might pass the Huntington’s gene on to their children. These people may consider genetic testing and family planning options.
Talk to your GP if you are planning to become pregnant and:
you have a family history of Huntington’s disease
a test has shown that you have the genetic defect that causes the condition
This could mean that your child is at risk of developing Huntington’s disease.
Your GP can refer you to a genetic counselor to discuss your options.
These may include:
- have a child with a donor egg or sperm
- adopt a child
- have a test during pregnancy (chorionic villus sampling) to see – if your baby will have Huntington’s disease
- preimplantation genetic diagnosis: eggs are fertilized in the laboratory and tested to make sure they do not have the Huntington’s disease gene, before being implanted in the uterus
Katherine Johnson, M.D., is a board-certified obstetrician-gynecologist with clinical expertise in general obstetrics and gynecology, family planning, women’s health, and gynecology.
She is affiliated with the Obstetrics and Gynecology division at an undisclosed healthcare institution and the online platform, Maternicity.com.