MLH1 and colorectal cancer: Lynch syndrome is caused by a germline mutation in one of the DNA mismatch repair (MMR) genes MLH1, MSH2, MSH6 and PMS2 or a deletion in EPCAM. 1–5 Lynch syndrome is estimated to be present in one in 279 people in the general population6 and to cause ~2–5% of all colorectal cancers.7,8 People with Lynch syndrome are at increased risk of various types of cancers, mainly colorectal cancer.