Lynch syndrome arises from inherited mutations, known as pathogenic variants, in the genes encoding the proteins of the highly conserved DNA mismatch repair (MMR) system: mutL homolog 1 (MLH1), mutS homolog 2 (MSH2), mutS homolog 6 (MSH6) and PMS1 homolog 2 (PMS2).6 Here, MLH1 is linked to Lynch syndrome.