PMS2 and Leigh syndrome: Lynch syndrome (LS, MIM: 120435) is one of the most prevalent autosomal dominant hereditary cancer susceptibility syndromes in humans and is caused by alterations in one of four mismatch repair (MMR) genes, namely, MLH1, MSH2, MSH6 and PMS2, or a structurally intact MSH2 epigenetic inactivation caused by a large deletion in the non-MMR gene epithelial cellular adhesion molecule (EPCAM)1,2.