Huntington’s disease is a brain disorder that affects how you move, think and feel. It is a genetic disease, which means it is passed down from parents to their children.
If you or someone you love has a family history of Huntington’s disease, understanding its causes, inheritance and risk factors can help you make informed decisions about your health.
Huntington’s disease is caused by a mutation (change) in a gene called HTT. This gene provides instructions for making a protein called huntingtin, which plays a role in how a brain works.
When the HTT gene works correctly, it helps nerve cells in the brain function properly. When a mutation occurs, the huntingtin protein becomes toxic and damages brain cells over time.
The HTT gene mutation happens in a DNA segment known as the CAG repeat. In a healthy person, this section repeats between 10 and 35 times. But in someone with Huntington’s disease, it repeats 40 or more times.
The more repeats there are, the earlier symptoms may start. The increase leads to the breakdown of brain cells, which causes the physical, cognitive and emotional symptoms of the disease.
Learn more about how your genes can affect your brain health.
Huntington’s disease is inherited, meaning it’s passed down from parents to children. It follows an autosomal dominant inheritance pattern. This means that a person only needs to inherit one copy of the mutated HTT gene from a parent to develop the disease.
Each child of a parent with Huntington’s disease has a 50% chance of inheriting the faulty gene. If they inherit it, they will eventually develop the disease. If they do not inherit the mutation, they will not get Huntington’s and cannot pass it on to their own children. The disease does not skip generations.
The biggest risk factor for Huntington’s disease is having a parent with the condition. If one of your parents has it, you are at risk of inheriting the gene. But there are some variations in when and how symptoms develop.
Most people with Huntington’s start noticing symptoms between the ages of 30 and 50. But some develop the disease much earlier or later:
Some other factors that may influence when symptoms begin or how quickly they progress include:
If you have a family history of Huntington’s disease, you might wonder if you should get tested. A genetic test can tell you if you have the mutated HTT gene and how many CAG repeats you have.
Getting tested is a personal choice that comes with emotional, medical and practical considerations. You may want to consider testing if you:
Because genetic testing is a big decision, talking to a genetic counselor before and after testing can help. If Huntington’s disease runs in your family, a genetic counselor can help you understand your risk, decide if testing is right for you and help you plan for the future. A counselor can also explain what the results mean, answer your questions, help you cope with your emotions and offer support resources.
If you don’t know your family history, genetic counselors can also help you navigate this uncertainty and offer support in making decisions about testing.
Talk to your health care provider to learn more about genetic testing and if it might be right for you.
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