Predisposition to LS is due to germline mutations in DNA mismatch repair (MMR) genes (MLH1, MSH2, MSH6, and PMS2) [6] or deletion in EPCAM gene leading to transcriptional silencing by MSH2 hypermethylation [7], whereas germline mutations in the APC gene underlie FAP [8]. This evidence concerns the gene MSH2 and Leigh syndrome.