Huntington Disease

Huntington disease is an autosomal-dominant neurodegenerative disorder caused by an expanded CAG trinucleotide repeat in the HTT gene. The abnormal huntingtin protein progressively damages medium spiny neurons in the striatum and contributes to cortical degeneration. As these motor circuits lose their ability to regulate movement, the patient may first develop chorea—irregular, flowing, involuntary movements—and later develop bradykinesia, rigidity, or dystonia. The disease is not only a movement disorder. Degeneration across cortical and subcortical networks produces a changing combination of: - Motor findings: chorea, impaired coordination, dystonia, rigidity, slowed movement, gait instability, and falls. - Cognitive findings: impaired executive function, slowed processing, poor judgement, and eventual loss of functional independence. - Psychiatric findings: depression, irritability, apathy, impulsivity, anxiety, or psychosis. The motor pattern can mislead inexperienced observers. A person may appear physically restless early in the illness, yet be unable to transfer safely or manage a meal. Later, chorea may become less prominent while rigidity, dystonia, and immobility increase. Fall risk therefore persists throughout the illness, although the reason for the risk changes. Dysphagia becomes a major threat as motor control...