Huntingtons Disease (HD)/Huntingtons Chorea:
Autosomal dominant, chronic progressive degenerative disorder of CNS characterised by involuntary movements (predominantly chorea) with behaviour and psychological changes. Gene located on short arm of chromosome four – have abnormally long sequences or ‘repeats’ of coded instructions. Estimated prevalence of 4-10/100 000 (very low in Japan). M=F. First presents during ages 35-50 many families completed before onset of symptoms pass on genes; juvenile variant may develop before age 20 (3%). Carriers have 50% chance of passing on gene.
Brain shrinks and is atrophied. Due to progressive atrophy and degeneration of the caudate nucleus within the basal ganglia results in loss of specific sets of cholinergic neurons and neurons that synthesise gamma-aminobutyric acid (GABA).
Clinical features:
Develop insidiously and vary in type, severity and progression; develop progressive dementia, mood and personality changes associated with involuntary choreiform movements – initially starts with slight clumsiness that progresses to restlessness/’fidgeting’ of fingers and toes with facial grimacing. May start or progress to bipolar or schizophrenic disorder. Antisocial behaviour may be first manifestation. Diagnosis confirmed with decrease in GABA concentrations in caudate nucleus; confirmatory genetic testing can be used in absence of family history.
Movement disorders:
Involuntary – chorea – arrhythmic and irregular; usually appear first in the toes; patient may be able to consciously resist for a while; progress to affect activities
Voluntary – “motor impersistence” eg unable to do several voluntary tasks at the same time (eg cannot hold arms out, protrude tongue and keep eyes shut at the same time) may be unsafe to drive due to inability to carry out all task simultaneously for safe driving; voluntary movements also impaired by rigidity, bradykinesia and dystonia
Gait – wide base, ataxic, lurches (due to chorea)
Dysphagia is common
In advanced stages – unable to ambulate; cease talking; unable to care for self.
Life threatening complications – falls; infections; choking; pneumonia.
Treatment:
Genetic testing and counselling essential. No form of treatment shown to be effective; dopamine antagonists for symptomatic treatment; antipsychotics can suppress choreic movements and agitated behaviours; psychosocial support; occupational and speech therapy; adequate nutrition; most die within 10-20 (mean of 17) years from onset of symptoms (8-10 years for juvenile form).
https://www.ncbi.nlm.nih.gov/pubmed/28851209
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