Hereditary cancer predisposition syndromes are caused by pathogenic variants (also called mutations) in a gene that is normally supposed to protect people from developing cancer. These are germline mutations that either arise spontaneously during conception (de novo) or are inherited from a parent.

The majority of hereditary cancer predisposition syndromes, including Lynch syndrome, follow autosomal-dominant inheritance, meaning the mutation only has to be passed down to offspring from one parent, not both, in order for a child to inherit the cancer predisposition syndrome.

With autosomal-dominant inheritance, when a hereditary cancer predisposition syndrome is identified in an individual, their parents, children and siblings (first degree relatives) each have a 50% chance of also having inherited that condition. An exception to this is de novo mutations, which would only give an individual's children a 50% chance of inheriting the condition, not their siblings or parents.

If you have a patient with a hereditary cancer predisposition syndrome, this factsheet is patient-friendly and covers Cancer Genetics Basics.

Lynch syndrome is a hereditary cancer predisposition syndrome. About 1-3% of colorectal cancers and 0.8-1.4% of endometrial cancers can be attributed to Lynch Syndrome. Current estimates are that 1 in 300-440 individuals in the general population have Lynch syndrome.