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Huntington's disease

 

Huntington's disease is a hereditary brain disorder caused by a faulty gene. The gene gradually causes the death of brain cells responsible for movement and thought.

 

The last five years have been tremendously exciting, as scientist’s basic knowledge of Huntington's disease has expanded. Now the big challenge is to transform these discoveries into treatments.

 

How do you get Huntington's disease?

Huntington's disease is caused by a faulty gene, which is passed from parent to child. The faulty gene makes a faulty protein called 'huntingtin'. Scientists throughout the world are working to find out exactly what this protein does.

 

Each person whose parent has Huntington's disease is born with a 50-50 chance of inheriting the faulty gene on chromosome 4 . Anyone who inherits the gene will at some stage develop the disease.

 


What are the symptoms?

The symptoms of Huntington's disease (HD) usually develop when people are between 30-50 years old. At first, there are jerky, uncontrollable muscle movements of the arms, legs, body and face, as well as stumbling and clumsiness, lack of concentration, short-term memory lapses and depression. Early symptoms can also include personality changes such as apathy, irritability and mood swings.

 

As the disease progresses, these symptoms worsen. Involuntary movements increase and people have difficulty speaking and swallowing. Eventually, full nursing care is needed.

 

Which parts of the brain are affected?

The faulty gene creates a faulty protein, which somehow damages nerve cells in two main areas of the brain - the basal ganglia and the cerebral cortex.

 

The basal ganglia is involved in movement and the cortex is involved in thinking. The death of brain cells in both areas leads to gradual physical, mental and emotional changes.

 

The major scientific breakthroughs

These began in 1983 when scientists discovered the HD mutation on chromosome 4. Ten years later they discovered that people with HD had a repeating part of their DNA called ‘CAG repeats’ and a genetic test was developed.

 

Research into Huntington's exploded in 1996, when scientists inserted the faulty gene into a mouse. The mouse developed HD allowing scientists to test new therapies and drugs.

 

The ethics

The genetic test shows whether you will get the disorder in the future. The test is available to people over 18.

 

Unlike many other genetic tests which show a susceptibility the HD test shows you will get HD sometime between the age of 30 and 50.

 

This raises a number of ethical issues:

  • Should mortgage and life insurance companies have a right to know the results of your test? More info
  • If juvenile HD is suspected, should parents be able to agree to their child being tested? More info
  • What if your grandparent has HD, your mum doesn’t want to know if she has the gene - and you want to be tested. Your results would tell your mum whether she carries the gene.