MSH2 and Leigh syndrome: LS is a result of pathogenic germline variants in four DNA mismatch repair (MMR) genes (MLH1, MSH2, MSH6 and PMS2) or by epigenetic inactivation of MSH2 due to a deletion at the 3’ end of EPCAM2–6, but an obvious pre-malignant phenotype/genotype correlation is not evident.