LS is caused by pathogenic variants in mismatch repair (MMR) genes MLH1, MSH2, MSH6, and PMS2, as well as deletions in EPCAM which lead to silencing of MSH2. Affected individuals are at increased risk for colorectal cancer (CRC), endometrial cancer, ovarian cancer, and other cancers (Lindor et al., 2008; Senter et al., 2008; Baglietto et al., 2010; Bonadona et al., 2011; Giardiello et al., 2014). The gene discussed is MSH2; the disease is Leigh syndrome.