In humans, heterozygous pathogenic germline variants in four MMR genes (MLH1, MSH2, MSH6, and PMS2) or heterozygous germline deletions of the EPCAM gene are causative for Lynch syndrome (LS; also known as hereditary non-polyposis colorectal cancer, HNPCC). The gene discussed is PMS2; the disease is hereditary nonpolyposis colon cancer.