The gene that causes Huntington's disease could affect more than 10 times as many people than previously thought, scientists believe.
A new study has shown that the gene linked to the brain disorder is more common in the general population, with up to 1 in 400 people potentially at risk of developing the condition.
It was previously thought Huntington's affected about 1 in 5,000 of the population.
The research was carried out by teams from Aberdeen University, the University of British Columbia and the Coriell Institute for Medical Research in the US, and suggests the condition is being missed by doctors in older people.
Huntington's is an incurable genetic condition that usually starts between the ages of 35 and 45, and sees changes to muscle control that slowly erodes mobility and the ability to talk.
The gene in question has a section where three letters of the DNA code are repeated. People with more than 40 repeats develop the disease, as do some of those with 37 to 39 repeats.
Until now it was not known just how many people in the general population have 37 to 39 repeats, which usually results in Huntington's disease starting over the age of 60.
John Eden, chief executive of the Scottish Huntington's Association, said: "These results may mean we are seriously underestimating the number of elderly patients with the condition.
"Their symptoms may not be clearly recognised as Huntington's disease, meaning there could be a whole generation of their children potentially at risk and they do not even realise it."
The study was published in Neurology, the journal of the American Academy of Neurology.
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