Lynch syndrome (LS) is caused by pathogenic variants in any of the four mismatch repair genes, MLH1, MSH2, MSH6 or PMS2 or by deletion of the 3′end of EPCAM (TACSTD1) which results in hypermethylation of the MSH2 promoter (path_MMR).1 The gene discussed is MSH2; the disease is Leigh syndrome.