MLH1 and Leigh syndrome: In this study, two significant mutations were identified in two typical families with LS: one novel mutation in the MSH2 gene (NM_000251.2:c.1486delT:p.L496*), which was not recorded in any database including GnomAD; and a previously known mutation in the MLH1 gene (NM_001258271.1:c.884 + 4A > G), which was very rare and the mutation frequency was not recorded in any database including GnomAD.