It is very possible that you haven’t heard of Huntington's disease before, or met somebody with Huntington's disease. This is because it is a rare disease with less than 20,000 cases per year seen in the UK. However, chances are, if you know one person with Huntington's disease, you know of more than one person because of the genetic nature of Huntington's disease which means that a child of someone with Huntington's disease has 50% of inheriting it. They can have Huntington's disease and it is possible that in one family a child’s parent and a grandparent has Huntington's disease, their siblings and aunties or uncles and cousins.
For more information about Huntington's disease, the Huntington's disease Association has lots more useful and informative resources about Huntington's disease on their website.