Lynch syndrome (LS) is an autosomal dominant disorder due to germline pathogenic variants in DNA mismatch repair (MMR) genes includingMLH1,MSH2,MSH6,and post-meiotic segregation increased 2 (PMS2).1, 2, 3, 4TheEpCam,a neighboring gene of MSH2, is also responsible for LS. The gene discussed is MSH2; the disease is Leigh syndrome.