Huntington's Disease

Question 1

What is huntington’s disease?

Genetics

Answer 1

Huntington’s chorea is an AUTOSOMAL DOMINANT genetic condition that causes a progressive deterioration in the nervous system.

Huntington’s chorea is a “trinucleotide repeat disorder” that involves a genetic mutation in the HTT gene on chromosome 4.

Question 2

What genetic phenomenon does huntington’s demonstrate?

Answer 2

Huntington’s chorea displays something called genetic “anticipation”. Anticipation is a feature of trinucleotide repeat disorders.

This is where successive generations have more repeats in the gene, resulting in:

• Earlier age of onset
• Increased severity of disease

Question 3

Clinical Features

Answer 3

Huntington’s chorea usually presents with an insidious, progressive worsening of symptoms.

It typically begins with cognitive, psychiatric or mood problems. These are followed by the development of movement disorders.

Patients are usually asymptomatic until symptoms begin around aged 30 to 50.

Chorea (involuntary, abnormal movements)
Eye movement disorders
Speech difficulties (dysarthria)
Swallowing difficulties (dysphagia)

Question 4

Diagnosis

Answer 4

Diagnosis is made in a specialist genetic centre using a genetic test for the faulty gene.

It involves pre-test and post-test counselling regarding the implications of the results.

MRI = shows atrophy of caudate nucleus and putamen

Question 5

Management

Answer 5

There are currently no treatment options for slowing or stopping the progression of the disease.

The key to management of the condition is supporting the person and their family.

• Involvement of MDT in supporting and maintaining their quality of life (e.g. occupational therapy, physiotherapy and psychology)
• Speech and language therapy where there are speech and swallowing difficulties
• Genetic counselling regarding relatives, pregnancy and children
• Advanced directives to document the patients wishes as the disease progresses
• End of life care planning
• Medical treatment is based on symptomatic relief. As the disease progresses medication requirements may change. It is important to discontinue unnecessary medication to minimise adverse effects.

Medications that can suppress the disordered movement:

• Antipsychotics (e.g. olanzapine)
• Benzodiazepines (e.g. diazepam)
• Dopamine-depleting agents (e.g. tetrabenazine)
• Depression can be treated with antidepressants.

Question 6

Prognosis

Answer 6

Huntington’s chorea is a progressive condition.

Life expectance is around 15-20 years after the onset of symptoms. As the disease progresses patients become more susceptible and less able to fight off illnesses. Death is often due to respiratory disease (e.g. pneumonia). Suicide is a more common cause of death than in the general population.