Lynch syndrome, often called hereditary non-polyposis colorectal cancer (HNPCC), is an inherited disorder that increases the risk of many types of cancer, particularly cancers of the colon (large intestine) and rectum, which are collectively referred to as colorectal cancer.
People with Lynch syndrome also have an increased risk of cancers of the stomach, small intestine, urinary tract. Additionally, women with this disorder have a high risk of cancer of the ovaries and lining of the uterus (the endometrium).
Prevalence
Approximately 3 to 5 percent of these cancers are caused by Lynch syndrome.
Genetics
Variations in the MLH1, MSH2, MSH6, PMS2, or EPCAM gene increase the risk of developing Lynch syndrome. The MLH1, MSH2, MSH6, and PMS2 genes are involved in the repair of mistakes that occur when DNA is copied in preparation for cell division (a process called DNA replication). Mutations in any of these genes prevent the proper repair of DNA replication mistakes. As the abnormal cells continue to divide, the accumulated mistakes can lead to uncontrolled cell growth and possibly cancer.
How is Lynch syndrome inherited?
Lynch syndrome cancer risk is inherited in an autosomal dominant pattern, which means one inherited copy of the altered gene in each cell is sufficient to increase cancer risk. It is important to note that people inherit an increased risk of cancer, not the disease itself. Not all people who inherit mutations in these genes will develop cancer.
How is Lynch syndrome diagnosed?
A strong family history of colorectal cancer, or any of the other cancers (stomach, ovary, urinary, ovarian or endometrial) in young relatives (less than fifty years of age), across a number of generations raises the suspicion of Lynch Syndrome. Loss of normal staining pattern in the cells of abnormal polyps or cancers can also suggest Lynch syndrome and direct further definitive testing for the known genetic mutations seen in Lynch syndrome.
How is cancer prevented in Lynch syndrome?
Regular gastroscopy and colonoscopy are needed to remove polyps or detect cancer early from the gastrointestinal tract. Sometimes preventative (prophylactic) total colectomy surgery is needed. Close surveillance for other non-gastrointestinal cancer is also required.
