It is caused by germline mutations in the DNA mismatch repair genes MLH1, MSH2, MSH6 or PMS2. In a subset of patients, Lynch syndrome is caused by 3' end deletions of the EPCAM gene, which can lead to epigenetic silencing of the closely linked MSH2. Relying solely on age and family history based criteria inaccurately identifies eligibility for Lynch syndrome screening or testing in 25%–70% of cases. The gene discussed is MLH1; the disease is Lynch syndrome.