huntington’s chorea

English: Charles Sabine, the NBC correspondent...

English: Charles Sabine, the NBC correspondent, at a Huntington’s Disease conference in Prague (Photo credit: Wikipedia)

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Modified version of Image:Autosomal Dominant P...

Modified version of Image:Autosomal Dominant Pedigree Chart.svg. Enlarged letters, cropped. Its description is: Autosomal Dominant Pedigree Chart. In Autosomal Dominance the chance of receiving and expressing a particular gene is 50% regardless of the sex of parent or child. (Photo credit: Wikipedia)

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English: Front page of George Huntington's com...

English: Front page of George Huntington’s communication, “On Chorea” (Photo credit: Wikipedia)

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English: Coronal FSPGR through the brain at th...

English: Coronal FSPGR through the brain at the level of the caudate nuclei demonstrating marked reduced volume in keeping with the patient’s known diagnosis of Huntington Disease. Image from Radiopaedia.org case here (Photo credit: Wikipedia)

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English: Huntington's Disease: Autopsy case, i...

English: Huntington’s Disease: Autopsy case, immunohistochemical staining for ubiquitin reveals mutliple inclusions in the caudate nucleus (Photo credit: Wikipedia)

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English: Front page of George Huntington's com...

English: Front page of George Huntington’s communication, “On Chorea”; on the right is an 1872 photo of George Huntington (1850–1916), American physician (Photo credit: Wikipedia)

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English: Author - John Henkel, from the Food a...

English: Author – John Henkel, from the Food and Drug Administration Structures of brain: purple=caudate nucleus and putamen, orange=thalamus (Photo credit: Wikipedia)

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Poster of Recent studies of Huntington's disea...

Poster of Recent studies of Huntington’s disease Marjorie Guthrie lecture in genetics; 1985 (Photo credit: Wikipedia)

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(Huntington’s Chorea; Chronic Progressive Chorea; Hereditary Chorea) Huntington’s disease is an autosomal dominant disorder characterized by chorea and progressive cognitive deterioration, usually beginning in middle age. Diagnosis is by genetic testing. Treatment is supportive. First-degree relatives are encouraged to have genetic testing. Huntington’s disease affects both sexes equally. The caudate nucleus atrophies, the inhibitory medium spiny neurons in the corpus striatum degenerate, and levels of the neurotransmitters γ-aminobutyric acid (GABA) and substance P decrease. Huntington’s disease results from a gene mutation causing abnormal repetition of the DNA sequence CAG that codes for the amino acid glutamine. The resulting gene product, a large protein called huntingtin, has an expanded stretch of polyglutamine residues, which leads to disease via unknown mechanisms. The more CAG repetitions, the earlier the disease begins and the more severe the effects. The number of repeats can increase with successive generations and, over time, lead to a more severe phenotype within a family tree. Symptoms and Signs Symptoms and signs develop insidiously, starting at about age 35 to 50 but can develop before adulthood. Dementia or psychiatric disturbances (eg, depression, apathy, irritability, anhedonia, antisocial behavior, full-blown bipolar or schizophreniform disorder) develop before or simultaneously with the movement disorder. Abnormal movements appear; they include myoclonic jerks or irregular movements of the extremities, a lilting gait (like a puppet’s), facial grimacing, ataxia, and inability to sustain a motor act (motor impersistence) such as tongue protrusion. The disorder progresses, making walking impossible, swallowing difficult, and dementia severe. Most patients eventually require institutionalization. Death usually occurs 13 to 15 yr after symptoms begin. The cause is usually pneumonia or coronary artery disease Diagnosis Clinical evaluation, confirmed by genetic testing MRI to rule out other causes Diagnosis is based on typical symptoms and signs plus a positive family history and is confirmed by genetic testing. Neuroimaging is done to exclude other disorders; in advanced Huntington’s disease, MRI and CT coronal views show boxcar ventricles (ie, squared-off edges due to atrophy of the caudate head). Treatment Supportive measures Genetic counseling Because the disease is progressive, end-of-life care should be discussed early (see The Dying Patient). Treatment is supportive. Chorea and agitation may be partially suppressed by antipsychotics (eg, chlorpromazine 25 to 300 mg po tid, haloperidol 5 to 45 mg po bid); dose is increased until intolerable or undesirable adverse effects (eg, lethargy, parkinsonism) occur. Alternatively, tetrabenazine may be used. The dose is started at 12.5 mg po once/day; dosage is increased (to 12.5 mg bid in the 2nd wk, 12.5 mg tid in the 3rd wk, up to a total of 100 mg/day divided into 3 doses) until intolerable adverse effects (eg, sedation, akathisias, parkinsonism, depression) occur or chorea resolves. Experimental therapies aim to reduce glutamatergic neurotransmission via the N-methyl-d-aspartate receptor and bolster mitochondrial energy production. Treatment to supplement GABA in the brain has been ineffective. People who have 1st-degree relatives with the disease should have genetic testing and counseling (see also Prenatal Genetic Counseling and Evaluation) because people are likely to have children before symptoms appear. If such people are interested in testing, they are referred to centers that have expertise in dealing with the complex ethical and psychologic issues involved.

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