Who is huntingtons disease named after

In , a collaborative group of investigators discovered the gene that causes HD. As a result of this discovery it is now possible to diagnose HD with blood or tissue samples. HD is caused by mutation in a gene located on chromosome 4. This gene is found in every human being, and contains a CAG repeat sequence.

We have not yet discovered the gene's normal function. The larger the number of triplet repeats, generally speaking, the earlier in life one will develop HD. Furthermore, when the gene is passed from father to child but not when passed from mother to child the gene may lengthen even more, resulting in an earlier age of onset for the disease.

This phenomenon is known as anticipation. Genes for diseases can be either dominant or recessive. The gene for HD is dominant. On the other hand, if people with a parent suffering from HD do not inherit the mutant gene, they cannot pass it on to anyone else. It is important to understand that while people are born with the mutated gene for HD, in most cases they will not develop the symptoms until later in life.

Therefore someone can be without symptoms or presymptomatic for a number of years. In the past, there was no way to test for the abnormal gene, but now a blood test can determine whether or not an individual carries the gene for HD. This test can be used in cases of suspected HD, to confirm the diagnosis, or it can be used as a predictive test in individuals who are at risk for HD.

Researchers are working on getting a better understanding of the underlying disease causing mechanisms to develop disease modifying therapies. What is the underlying cause of HD? In , scientists identified the mutation that causes HD. The HTT gene is located on chromosome 4 and encodes a protein called huntingtin. The gene contains a sequence of three nucleotides the basic units of DNA , cytosine-adenine-guanine CAG , that is repeated several times.

This so-called trinucleotide repeat can vary in length. Since the expansion that causes HD is present in all cells of the body from conception, and can be passed on to subsequent generations, HD is a hereditary disease. The Huntingtin gene HTT is located on chromosome 4. This means that the number of repeats in this section can increase or decrease when it is passed down to the next generation.

If the number of repeats is between 27 and 35 the so-called intermediate repeat length , that individual will not develop HD and the section is considered normal. However, a CAG repeat number of 27 or more is unstable and liable to increase when passed on to the next generation, meaning that those children carry a risk of developing HD.

Individuals with a CAG repeat number between 36 and 39 may develop HD, but only very late in life, if at all. This is known as the reduced-penetrance repeat length range. When the number of CAG repeats is higher than 39, a person will develop HD within a normal lifespan — most often in mid-adult life. In rare cases the CAG expansion can be exceptionally long, leading to disease onset in adolescence or childhood juvenile HD.

Patients who develop the disease before the age of 10 often have more than 80 CAG repeats. CAG repeat length Disease causing? Consequences for offspring? What is a gene? Genes are found on our chromosomes inside every cell in our body. Most usually, everyone inherits two copies of each gene — one from the mother, one from the father. The parent himself may already have the disease or this can develop later in age. Genes are located along the length of the chromosomes like beads on a string depicted as coloured lines.

Most usually everyone inherits two copies of each gene — one from the mother and one from the father. What is a protein? Proteins are large molecules made up of building blocks called amino acids. The exact sequence of amino acids in a particular protein is determined by the DNA sequence of the corresponding gene.

Genes therefore function as blueprints — sets of instructions to cells that tell them how to build specific proteins. The HTT gene contains instructions on how to build the huntingtin protein. Proteins are the molecules that do the work inside cells — they perform a large number of essential processes, such as enzyme reactions or structural support. If a protein functions abnormally or is missing due to an expansion in the gene that encodes it, then it can affect the cell and, ultimately, the whole organism, sometimes causing disease.

The huntingtin protein. Huntingtin seems to be a very important protein because the absence of it is lethal to mouse embryos. At one particular end of the huntingtin protein there is a stretch of repeats of one particular amino acid called glutamine. This distinctive feature, known as the polyglutamine repeat, normally consists of up to 35 glutamine units. In people who carry the HD expansion, however, it contains at least 36 repeats and it is this polyglutamine expansion that results in a protein that malfunctions.

How is HD passed on? HD is a dominant hereditary disease. Medical techniques can ensure that an affected individual only passes on the normal HTT gene to his or her children. On the other hand, a person who has not inherited the mutant HTT gene will not develop the disease, and his or her children will not be at risk of it either.

The HD expansion cannot skip a generation. However, it can happen that an expansion carrier dies before showing symptoms, and that his or her children do not realise they are at risk of developing the disease. Brain areas involved in HD. Certain functions of the brain such as the ability to move, think and talk gradually deteriorate in HD as crucial nerve cells become damaged and die. The striatum is primarily involved in planning and controlling movements, but also in many other processes, including cognition and emotions.

As HD progresses, it affects the cortex the outermost wrinkled part of the brain , contributing to cognitive deterioration. HD In Daily Life. How does HD affect daily life? Young adults in particular may need to consider the implications of a positive test result for their education, training and employment. Working, social life and general daily activities become problematic, and patients become increasingly dependent on help from relatives and health and social care professionals.

Local patient advocacy groups and clinical centres can be contacted at any time, and will provide support. Are there any strategies for coping better with HD? Efficient strategies for coping with HD have to be personalised and depend on the affected person, the stage of the disease and the family context.

HD develops very slowly, so that in general there is time to adapt to the changes it brings about. For carers and loved ones, a better understanding of the behavioural and cognitive impairments associated with the disease may help them to develop strategies for accommodating these changes and maintaining a good relationship with the affected person.

Helpful information and advice is available from HD specialists and patient advocacy groups. If you go to this page you will find a list of language area coordinators who can help you. Alternatively, you may use the contact form provided here.

How do I get an appointment with a specialist? This differs from one European country to another but most often you need to obtain a referral from your general practitioner before you can see a specialist doctor.

However, the exact mechanisms by which mutant huntingtin protein leads to damage in the brain are still being explored. The symptoms vary , both from person to person and within any one individual throughout the course of the disease. Progressive in nature, the disease symptoms get worse over time. Individuals with JHD frequently experience muscle stiffness and seizures instead of chorea, and about one in three JHD patients experiences seizures.

Genetic testing for a mutation of the HTT gene can help doctors determine whether a person will develop the disease. Nonetheless, existing medications may help patients manage their symptoms and improve their quality of life.