Despite the negative results of the study, it doesn't exclude the possibility of Lynch syndrome for 100%, and its presence may be caused by the mutations of other genes (PMS1, PMS2 and MLH3), responsible for DNA repair.
Since the discovery of the major human genes with DNA mismatch repair function, mutations in five of them have been correlated with susceptibility to Lynch syndrome: mutS homolog 2 (MSH2); mutL homolog 1 (MLH1); mutS homolog 6 (MSH6); postmeiotic segregation increased 2 (PMS2); and postmeiotic segregation increased 1 (PMS1).
Two additional MMR genes, MLH3 and PMS1, have also been proposed to play a role in Lynch syndrome predisposition, but the clinical significance of mutations in these genes is less clear.