Huntington Disease (HD) is a hereditary neurological disorder that shows a gene expansion associated with trinucleotide repeats.


Inheritance: autosomal dominant, with inheritance of a single affected allele sufficient to cause disease


Chromosome location: 4p16.3


Gene affected:HTT (Huntingtin)


Clinical features:

(1) onset during adulthood, usually after 35 years of age

(2) abnormal movements (Parkinsonism, dysarthria, hyperreflexia, tremor, chorea, incoordination, abnormal eye movements, etc)

(3) voluntary movements may be affected

(4) emotional disorder (depression, apathy, irritability. psychosis, change in personality, disinhibition, etc)

(5) cognitive impairment progressing to dementia

(6) progressive with death within 10+ years

(7) complications may arise from repeated falls or from aspiration


Imaging studies show atrophy of the caudate and cerebral cortex.


Laboratory findings:

(1) >= 36 CAG repeats at HTT (CAG encodes glutamine, resulting in an expansion of the polyglutamine tract)


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