User:Ericksmd3839/Huntington's disease

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Huntington's disease has autosomal dominant inheritance, meaning that an affected individual typically inherits one copy of the gene with an expanded trinucleotide repeat (the mutant allele) from an affected parent. Since the penetrance of the mutation is very high, those who have a mutated copy of the gene will have the disease. In this type of inheritance pattern, each offspring of an affected individual has a 50% risk of inheriting the mutant allele, so are affected with the disorder (see figure). This probability is sex-independent. Sex-independent or sex-linked genes are traits that are found on the X or Y chromosomes.

Signs and symptoms of Huntington's disease most commonly become noticeable between the ages of 30 and 40 years, but they can begin at any age, and present as a triad of motor, cognitive, and psychiatric symptoms. When developed in an early stage it is known as juvenile Huntington's disease.

The most characteristic initial physical symptoms are jerky, random, and uncontrollable movements called chorea. Many people are not aware of their involuntary movements, or impeded by them. Chorea may be initially exhibited as general restlessness, small unintentionally initiated or uncompleted motions, lack of coordination, or slowed saccadic eye movements. These minor motor abnormalities usually precede more obvious signs of motor dysfunction by at least three years. The clear appearance of symptoms such as rigidity, writhing motions, or abnormal posturing appear as the disorder progresses. These are signs that the system in the brain that is responsible for movement has been affected. Psychomotor functions become increasingly impaired, such that any action that requires muscle control is affected. '''When muscle control is affected such as rigidity or muscle contracture this is known as dystonia. Dystonia is a neurological hyperkinetic movement disorder that results in twisting or repetitive movements, that may resemble a tremor.''' Common consequences are physical instability, abnormal facial expression, and difficulties chewing, swallowing, and speaking. Sleep disturbances and weight loss are also associated symptoms. Eating difficulties commonly cause weight loss and may lead to malnutrition. Weight loss is common in people with Huntington's disease, and progresses with the disease. Juvenile HD generally progresses at a faster rate with greater cognitive decline, and chorea is exhibited briefly, if at all; the Westphal variant of slowness of movement, rigidity, and tremors is more typical in juvenile HD, as are seizures.

Cognitive abilities are progressively impaired and tend to generally decline into dementia. Especially affected are executive functions, which include planning, cognitive flexibility, abstract thinking, rule acquisition, initiation of appropriate actions, and inhibition of inappropriate actions. Different cognitive impairments include difficulty focusing on tasks, lack of flexibility, a lack of impluse, a lack of awareness of one's own behaviors and abilities and difficulty learning or processing new information. As the disease progresses, memory deficits tend to appear. Reported impairments range from short-term memory deficits to long-term memory difficulties, including deficits in episodic (memory of one's life), procedural (memory of the body of how to perform an activity), and working memory.

Reported neuropsychiatric signs are anxiety, depression, a reduced display of emotions, egocentrism, aggression, and compulsive behavior, the latter of which can cause or worsen addictions, including alcoholism, gambling, and hypersexuality. Other common psychiartic diorders could include obsessive-compulsive disorder, mania, insomnia and bipolar disorder. Difficulties in recognizing other people's negative expressions have also been observed. The prevalence of these symptoms is highly variable between studies, with estimated rates for lifetime prevalence of psychiatric disorders between 33 and 76%. For many with the disease and their families, these symptoms are among the most distressing aspects of the disease, often affecting daily functioning and constituting reason for institutionalization. Early behavioral changes in HD result in an increased risk of suicide. Often, individuals have reduced awareness of chorea, cognitive, and emotional impairments.

Life expectancy in HD is generally around 10 to 30 years following the onset of visible symptoms. Whereas juvenile Huntington's disease has a life expectancy rate of 10 years after onset of visible systems. Most life-threatening complications result from muscle coordination, and to a lesser extent, behavioral changes induced by declining cognitive function. The largest risk is pneumonia, which causes death in one third of those with HD. As the ability to synchronize movements deteriorates, difficulty clearing the lungs, and an increased risk of aspirating food or drink both increase the risk of contracting pneumonia. The second-greatest risk is heart disease, which causes almost a quarter of fatalities of those with HD. Suicide is the third greatest cause of fatalities, with 7.3% of those with HD taking their own lives and up to 27% attempting to do so. To what extent suicidal thoughts are influenced by behavioral symptoms is unclear, as they signify a desire to avoid the later stages of the disease. Suicide is the greatest risk of this disease before the diagnosis is made and in the middle stages of development throughout the disease. Other associated risks include choking; due to the inability to swallow, physical injury from falls, and malnutrition.

In 2020 there were 197 clinical trials related to varied therapies and biomarkers for Huntington's disease listed as either underway, recruiting or newly completed. Compounds trialled, that have failed to prevent or slow the progression of Huntington's disease include remacemide, coenzyme Q10, riluzole, creatine, minocycline, ethyl-EPA, phenylbutyrate and dimebon. '''In April of 2022 The Huntington's Disease Clinical Trials Corner completed clinical trials for Huntington's Disease which is sponsored and funded by Novartis Pharmaceuticals. This study used VIBRANT-HD which had participants of a 4:1 active control rate with usage of double-blind, placebo-controlled, multiple-dose design with three dose cohorts. Participants were followed up for 17 weeks with an additional 53 weeks by blinded dose. The study recruited in Canada, France, Germany, Hungary and Spain.'''

Embryos produced using in vitro fertilization may be genetically tested for HD using preimplantation genetic diagnosis. This technique, where one or two cells are extracted from a typically 4- to 8-cell embryo and then tested for the genetic abnormality, can then be used to ensure embryos affected with HD genes are not implanted, so any offspring will not inherit the disease. '''When the eggs are removed from the ovaries they are then fertilized with the fathers sperm and sent into a laboratory for testing of the Huntington gene. Only the embryos that test negative for the Huntington gene are then implanted into the mother's uterus.' Some forms of preimplantation genetic diagnosis—non-disclosure or exclusion testing—allow at-risk people to have HD-free offspring without'' revealing their own parental genotype, giving no information about whether they themselves are destined to develop HD. In exclusion testing, the embryo's DNA is compared with that of the parents and grandparents to avoid inheritance of the chromosomal region containing the HD gene from the affected grandparent. In nondisclosure testing, only disease-free embryos are replaced in the uterus while the parental genotype and hence parental risk for HD are never disclosed.

Tetrabenazine (Xenazine) was approved in 2000 for treatment of chorea in Huntington's disease in the EU, and in 2008 in the US. Although other drugs had been used "off label," tetrabenazine was the first approved treatment for Huntington's disease in the U.S. The compound has been known since the 1950s. An alternative to tetrabenazine is amantadine but there is limited evidence for its safety and efficacy. Xenazine as well as deutetrabenazine (Austedo) don't have any effect on the progression of the disease, however can help with controling the movement.

Article body
== https://www.genome.gov/genetics-glossary/Sex-Linked == Dystonia

https://www.mayoclinic.org/diseases-conditions/huntingtons-disease/symptoms-causes/syc-20356117

https://content.iospress.com/articles/journal-of-huntingtons-disease/jhd229002