Juvenile Huntington disease tends to progress more quickly than the adult-onset form; affected individuals usually live 10 to 15 years after signs and symptoms appear. Huntington disease affects an estimated 3 to 7 per , people of European ancestry.
Huntington's disease: the price paid for our big brains? – Science Weekly podcast
The disorder appears to be less common in some other populations, including people of Japanese, Chinese, and African descent. Mutations in the HTT gene cause Huntington disease. The HTT gene provides instructions for making a protein called huntingtin. Although the function of this protein is unknown, it appears to play an important role in nerve cells neurons in the brain.
This segment is made up of a series of three DNA building blocks cytosine, adenine, and guanine that appear multiple times in a row. Normally, the CAG segment is repeated 10 to 35 times within the gene.
In people with Huntington disease , the CAG segment is repeated 36 to more than times. People with 36 to 39 CAG repeats may or may not develop the signs and symptoms of Huntington disease , while people with 40 or more repeats almost always develop the disorder. An increase in the size of the CAG segment leads to the production of an abnormally long version of the huntingtin protein. The elongated protein is cut into smaller, toxic fragments that bind together and accumulate in neurons, disrupting the normal functions of these cells. The dysfunction and eventual death of neurons in certain areas of the brain underlie the signs and symptoms of Huntington disease.
This condition is inherited in an autosomal dominant pattern , which means one copy of the altered gene in each cell is sufficient to cause the disorder. An affected person usually inherits the altered gene from one affected parent. In rare cases, an individual with Huntington disease does not have a parent with the disorder. As the altered HTT gene is passed from one generation to the next, the size of the CAG trinucleotide repeat often increases in size. A larger number of repeats is usually associated with an earlier onset of signs and symptoms.
This phenomenon is called anticipation. People with the adult-onset form of Huntington disease typically have 40 to 50 CAG repeats in the HTT gene, while people with the juvenile form of the disorder tend to have more than 60 CAG repeats.
Individuals who have 27 to 35 CAG repeats in the HTT gene do not develop Huntington disease , but they are at risk of having children who will develop the disorder. As the gene is passed from parent to child, the size of the CAG trinucleotide repeat may lengthen into the range associated with Huntington disease 36 repeats or more. Bates GP.
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- Huntington's disease - Symptoms and causes - Mayo Clinic.
- Huntington’s disease.
History of genetic disease: the molecular genetics of Huntington disease - a history. Nat Rev Genet. Clinical characteristics of childhood-onset juvenile Huntington disease: report of 12 patients and review of the literature. For HD families, preimplantation genetic testing is possible and therefore to select embryos for transfer without the HD genetic mutation.
Prenatal testing is only done in situations where the mother would consider termination of the pregnancy should the fetus test positive. Otherwise, prenatal testing is the same as testing an asymptomatic child, which is not ethically recommended. In these cases, brain MRI can be useful in identifying an alternative diagnosis, such as ischemic infarction, pantothenate kinase-associated neurodegeneration, multiple sclerosis, neoplasm, or Creutzfeldt-Jakob disease. Otherwise, additional testing should be indicated based on medical and family history, physical and neurological exam.
The best care for patients with HD is provided by a multidisciplinary team of health professionals and supportive caregivers that addresses the broad physical and psychologic needs of patients and families, and manages new issues as they arise through long-term follow-up. Dopamine receptor blocking agents or dopamine depleting agents may be used if the chorea is disrupting quality of life.
Psychiatric symptoms such as depression, psychosis and agitation are similarly managed as any other psychiatric condition.
Huntington's disease - Illnesses & conditions | NHS inform
Stereotactic surgery DBS for severe and disabling cases of chorea has been reported. Investigational therapies such gene silencing through antisense oligonucleotide techniques are currently underway. Find more resources in the Education Roadmap. The International Parkinson and Movement Disorder Society MDS is a professional society of more than 8, clinicians, scientists and other healthcare professionals dedicated to improving the care of patients with movement disorders through education and research.
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