Overview
Huntington’s disease is an autosomal dominant neurodegenerative movement disorder characterised by chorea, dystonia, incoordination, and cognitive and behavioural dysfunction.
It is a trinucleotide repeat disorder and is caused by an expanded CAG repeat in the gene that codes for the huntingtin protein. It is progressive and incurable, leading to death over 15-20 years.
Anticipation can be seen in Huntington’s disease – this is where the signs and symptoms are more severe and present earlier in each following generation of offspring. This is due to more trinucleotide repeats arising (trinucleotide expansion).
Epidemiology
- Huntington’s disease is the most common genetic cause of chorea
- Mean age of onset is 30-50 years
Presentation
Patients with Huntington’s disease may have:
- Chorea – involuntary, brief and irregular muscle movements
- Behavioural changes – e.g. depression/irritability/apathy/mania
- Intellectual impairment and cognitive dysfunction:
- May include problems with focusing on tasks, planning, and impulsivity
- May also include disinhibition (an inability to suppress inappropriate behaviour)
- May include memory and mood problems
- Abnormal eye movements
- Rigidity
- Dystonia – abnormal muscle spasms and posturing
Differential Diagnoses
Sydenham’s chorea
- Usually seen in children/young adult
- There may be a preceding Streptococcal throat infection
- Other features of rheumatic fever
Tardive dyskinesia
- Usually seen after antipsychotic/metoclopramide use
- There is usually no family history
- Usually the muscles of the mouth are affected, but speech and swallowing are unaffected
Investigations and Diagnosis
Diagnosis is clinical
Genetic testing – CAG repeat testing
Management
There are unfortunately no treatments that slow the progression of the disease
- For chorea: consider tetrabenazine or atypical antipsychotics
Monitoring and Patient Advice
Monitoring
Patients are closely followed up, usually every 6-12 months or more often if new problems arise. It is important to remember to look for carer fatigue.
Patient Advice
Patients should be educated about the nature of Huntington’s disease and its genetics, and have discussions regarding family planning and further genetic testing.
Complications
Prognosis
- Death is usually from an associated condition such as pneumonia
- Suicide is the second most common cause of death
- Huntington’s disease is a progressive neurodegenerative disorder which usually leads to death within 15-20 years
- The more trinucleotide expansion there is, the worse the signs and symptoms are, the earlier the age of onset is, and the worse the prognosis is
