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Huntington disease (HD) is an autosomal dominant neurodegenerative disorder characterized by progressive motor and cognitive dysfunction and, frequently, psychiatric disorders.
- There is selective and progressive degeneration of the striatum, as well as atrophy of other brain regions as the disease progresses.
- Regional brain atrophy can be detected up to 15 years before diagnosable signs and symptoms are present.
- Onset of HD is progressive and insidious; generally occurring in mid-life (~45) though onset can range from infancy to late life.
- HD is a triplet repeat disorder, with an expansion of a CAG repeat in the gene “Huntingtin” (HTT) causing an expansion of a polyglutamine tract in the huntingtin protein.
- The length of the CAG repeat explains 50-70% of the variance in age of onset (the longer the repeat the earlier the onset), and also influences rate of progression (the longer the repeat, the faster the progression).
- HD is a fatal disorder for which there are no disease-modifying therapies.
- However, numerous effective symptomatic treatments are available.
- Cognitive impairment due to Huntington disease is classified under the neurocognitive disorders (NCDs) section of the Diagnostic and Statistical Manual of Mental Disorders, 5th Edition (DSM-5).