Question: What is (are) Huntington disease ?
Answer: Huntington disease (HD) is an inherited condition that causes progressive degeneration of neurons in the brain. Signs and symptoms usually develop between ages 35 to 44 years and may include uncontrolled movements, loss of intellectual abilities, and various emotional and psychiatric problems. People with HD usually live for about 15 to 20 years after the condition begins. It is caused by changes (mutations) in the HTT gene and is inherited in an autosomal dominant manner. Treatment is based on the symptoms present in each person and may include various medications. There is also a less common, early-onset form of HD which begins in childhood or adolescence. For more information on this form, please visit GARD's juvenile Huntington disease Web page.
Source: GARD

Question: What causes Huntington disease ?
Answer: What causes Huntington disease? Huntington disease (HD) is caused by a change (mutation) in the HTT gene. This gene gives instructions for making a protein called huntingtin. The exact function of this protein is unclear, but it appears to be important to nerve cells (neurons) in the brain. The HTT gene mutation that causes HD involves a DNA segment known as a CAG trinucleotide repeat. This segment is made up of three DNA building blocks that repeat multiple times in a row. The CAG segment in a normal HTT gene repeats about 10 to 35 times. In people with HD, it may repeat from 36 to over 120 times. People with 36 to 39 CAG repeats (an intermediate size) may or may not develop HD, while people with 40 or more repeats almost always develop HD. An increased number of CAG repeats leads to an abnormally long version of the huntingtin protein. The long protein is then cut into smaller, toxic pieces that end up sticking together and accumulating in neurons. This disrupts the function of the neurons, ultimately causing the features of HD.
Source: GARD

Question: Is Huntington disease inherited ?
Answer: How is Huntington disease inherited? Huntington disease (HD) is inherited in an autosomal dominant manner. This means that having a change (mutation) in only one of the 2 copies of the HTT gene is enough to cause the condition. When a person with HD has children, each child has a 50% (1 in 2) chance to inherit the mutated gene and develop the condition. Most people with HD have an affected parent. The family history can sometimes appear negative for various reasons even though a parent carries, or carried, a mutation in the HTT gene. In rare cases, HD is caused by a new (de novo) mutation in the HTT gene, in which case the disease occurs for the first time in the affected person and is not inherited from a parent. As HD is passed through generations, the size of the mutation in the HTT gene (called a trinucleotide repeat) often increases. A longer repeat in the HTT gene may cause earlier onset of symptoms. This phenomenon is called anticipation.
Source: GARD

Question: How to diagnose Huntington disease ?
Answer: Is genetic testing available for Huntington disease? Yes. Testing of adults at risk for Huntington disease (HD) who have no symptoms of the disease is called predictive testing. Whether to have predictive testing requires careful thought, including pre-test and post-test genetic counseling. This is particularly important because there is currently no cure. Furthermore, predictive testing cannot accurately predict the age a person with an HD mutation will develop symptoms, the severity or type of symptoms they will experience, or the future rate of disease progression. A person may want to have predictive testing because they feel they need to know, or to make personal decisions involving having children, finances, and/or career planning. Other people decide they do not want to know whether they will develop HD. Testing is appropriate to consider in symptomatic people of any age in a family with a confirmed diagnosis of HD. However, testing of asymptomatic people younger than age 18 is not considered appropriate. A main reason is that it takes away the choice of whether the person wants to know, while there is no major benefit to knowing at that age. People who are interested in learning more about genetic testing for HD should speak with a genetics professional. How is Huntington disease diagnosed? A diagnosis of Huntington disease is typically suspected in people with characteristic signs and symptoms of the condition and a family history consistent with autosomal dominant inheritance. The diagnosis can then be confirmed with genetic testing that identifies a specific type of change (mutation) in the HTT gene.
Source: GARD

Question: What are the treatments for Huntington disease ?
Answer: How might Huntington disease be treated? Unfortunately, there is currently no cure for Huntington disease (HD). The current goal of treatment is to slow down the course of the disease and help affected people function for as long and as comfortably as possible. Current treatment strategies involve the use of various medications to treat specific symptoms such as abnormal movements and behaviors. Depression and suicide are more common among affected people, so caregivers should monitor for associated symptoms and seek help if necessary. As symptoms of the disease worsen, affected people need more assistance, supervision, and care.
Source: GARD