Read more about this disease, some with Classification – Types – Signs and symptoms – Genetics – Pathophysiology – Diagnosis – Screening – Prevention – Treatment and management – Cures and much more, some including pictures and video when available.
Huntington’s disease, also called Huntington’s chorea, chorea major, or HD, is a genetic neurological disorder[1] characterized after onset by uncoordinated, jerky body movements and a decline in some mental abilities. These characteristics vary per individual, physical ones less so, but the differing decline in mental abilities can lead to a number of potential behavioral problems. The disorder itself isn’t fatal, but as symptoms progress, complications reducing life expectancy increase.[2] Research of HD has increased greatly in the last few decades, but its exact mechanism is unknown, so symptoms are managed individually.[3] Globally, up to 7 people in 100,000 have the disorder, although there are localized regions with a higher incidence.[4] Onset of physical symptoms occurs gradually and can begin at any age, although it is statistically most common in a person’s mid-forties (with a 30 year spread). If onset is before age twenty, the condition is classified as juvenile HD.[5]
The disorder is named after George Huntington, an American physician who published a remarkably accurate description in 1872.[6] In 1983 a marker for the altered DNA causing the disease was found,[7] followed a decade later by discovery of a single, causal, gene.[8] As it is caused by a single gene, an accurate genetic test for HD was developed; this was one of the first inherited genetic disorders for which such a test was possible. Due to the availability of this test, and similar characteristics with other neurological disorders, the amount of HD research has increased greatly in recent years.[9]
Huntington’s disease is one of several trinucleotide repeat disorders, caused by the length of a repeated section of a gene exceeding the normal range. The huntingtin gene (HTT) normally provides the information to produce Huntingtin protein, but when affected, produces mutant Huntingtin (mHTT) instead.[10]
Physical symptoms are usually the first to cause problems and to be noticed, but at this point they are usually accompanied by unrecognized cognitive and psychiatric ones. Almost everyone with Huntington’s disease eventually exhibits all physical symptoms, but cognitive and psychiatric symptoms can vary significantly between individuals.[2]
The most characteristic physical symptoms are jerky, random, and uncontrollable movements called chorea. In a few cases, very slow movement and stiffness (called bradykinesia and dystonia) occur instead, and often become more prominent than the chorea as the disorder progresses. Abnormal movements are initially exhibited as general lack of coordination, an unsteady gait and slurring of speech, but, as the disease progresses, any function that requires muscle control is affected, causing physical instability, abnormal facial expression, and difficulties chewing and swallowing. Eating difficulties commonly cause weight loss and may lead to malnutrition.[11][12] Associated symptoms involve sleep cycle disturbances, including insomnia and Rapid eye movement sleep alterations.[13][14] Juvenile HD generally progresses faster, is more likely to exhibit rigidity and bradykinesia, instead of chorea, and commonly includes seizures.[2]
Select cognitive abilities are impaired progressively. Especially affected are executive functions which include planning, cognitive flexibility, abstract thinking, rule acquisition, initiating appropriate actions and inhibiting inappropriate actions.[15] Psychomotor function, controlling muscles, perception and spatial skills, is also affected.[15] As the disease progresses, memory deficits tend to appear. Memory impairments reported 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.[15]
Psychiatric symptoms vary far more than cognitive and physical ones, and may include anxiety, depression, a reduced display of emotions (blunted affect), egocentrism, aggression, and compulsive behavior, which can cause, or worsen addictions, including alcoholism and gambling, or hypersexuality.[16][17] Difficulties in recognizing other people’s negative expressions has also been observed.[15][18]
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