A person’s risk of developing colorectal cancer is influenced by lifestyle factors, such as a low-fibre diet and lack of regular physical activity; however, as is the case with breast cancer, some inherited genetic variants increase the likelihood of a person developing colorectal cancer.
Lynch syndrome
A person who inherits Lynch syndrome will have a high lifetime risk of colorectal cancer, as well as increased risk of some other types of cancer. It can be caused by variants in one of four different genes (MLH1, MSH2, MSH6and PMS2) that code for essential DNA repair proteins.
In all four genes, only one affected copy is needed to cause the increased cancer risk. This means that Lynch syndrome is inherited in a dominant pattern in families.
People who have Lynch syndrome are generally advised to have a colonoscopy every two years so that cancers can be identified and removed at an early stage. For affected women, a hysterectomy and removal of the ovaried and fallopian tubes are often considered too, because there is a significant risk of endometrial and ovarian cancer.
Lynch Syndrome Ireland 