Being ‘at risk’ basically means that a person has a chance of inheriting the condition from their affected parent. This is because Huntington’s disease is a genetic condition, so anyone who has a parent with Huntington’s disease is at risk of inheriting the condition.
Huntington’s disease is hereditary – that means that it can be passed down, from parent to child, through genes in our DNA. Genes are passed to you from your parents – that’s why you might have blond hair like your dad, or brown eyes like your mother. We have thousands of genes, and they are all sectioned into different segments in our DNA. These segments are known as chromosomes and in total we have 23 pairs of chromosomes. The reason we have ‘pairs’ of chromosomes is because we inherit one from each parent.
Researchers discovered that the reason people develop Huntington’s disease is because of one gene, on chromosome 4, that is longer than it should be. The fact this gene is longer means that it eventually causes symptoms of Huntington’s disease. So, the gene can be described as ‘expanded’. Usually a person with Huntington’s disease has one expanded gene and one normal gene. A child of someone with Huntington’s disease will either inherit the expanded or the normal gene from that parent – and a normal gene from the other parent. That’s why there is a 50/50 chance (50% risk) of inheriting Huntington’s disease. Whether a person inherits the expanded or normal gene is purely down to chance, and that’s why you may hear people compare the risk for Huntington’s disease to the flip of a coin. Unfortunately if someone does inherit the gene that causes Huntington’s disease, then there is a risk of the gene being passed on to his or her future children as well.