LS is the most common hereditary condition predisposing to CRC and is caused by pathogenic germline variants in DNA mismatch repair (MMR) genes MLH1, MSH2, MSH6, and PMS2 [8] or, more rarely, deletions in the 3′ end of the EPCAM gene, leading to hypermethylation of the MSH2 gene promoter [9]. The gene discussed is MLH1; the disease is Leigh syndrome.