Hereditary nonpolyposis colorectal cancer, known as Lynch syndrome (LS), is an autosomal dominant hereditary disorder characterised by germline mutation in one of the four DNA mismatch repair (MMR) genes (MLH1, MSH2, MSH6, PMS2) or deletion of the EPCAM gene (resulting in MSH2 inactivation by promoter hypermethylation) [1]. The gene discussed is MSH2; the disease is hereditary nonpolyposis colon cancer.