Lynch syndrome (LS) is an autosomal-dominant disorder resulting from abnormalities in DNA mismatch repair genes and is associated with a heightened susceptibility to various types of malignancies.[1,2] In LS, approximately 90% of mutations are found in the MLH1 or MSH2 genes, whereas approximately 10% are attributed to the MSH6 and PMS2 genes. The gene discussed is MLH1; the disease is Leigh syndrome.