Lynch syndrome (LS) is an autosomal dominant inherited cancer susceptibility syndrome caused by germline pathogenic variants, such as DNA mismatch repair genes (MLH1, MSH2, MSH6, and PMS2) or germline deletion of the 3′ site of EPCAM, which is upstream of MSH2. It is characterized by a high risk of multiple synchronous and metachronous colorectal cancers. This evidence concerns the gene MSH2 and Leigh syndrome.