Accordingly, MLH1 and MSH2, which codify for the key proteins, are responsible for about 60–70% of the cases of LS, roughly evenly split, followed by MSH6, which accounts for 20–25%, PMS2 estimated in less than 15% of cases, and EPCAM linked to just 1–3% of the cases [35,36]. The gene discussed is MSH2; the disease is Leigh syndrome.