Pathogenic germline variants in MMR genes, causative for LS, were first discovered in the 1990s, with MSH2 being first (1993), followed by MLH1 (1994) and PMS2 (1994), MSH6 (1997), and EpCAM (2009) [2,3,4,5,6]. The gene discussed is MSH2; the disease is Leigh syndrome.