MSH6 and Leigh syndrome: A CTC1 heterozygous pathogenic nonsense variant (NM_025099.6:c.19C > T p. (Gln7Ter), Table 2) was found in a patient (ID 313) who had CRC with isolated loss of MSH6, as was diagnosed at age 48; the patient had no LS-related tumors in the family (Supplementary Table S2, Supplementary Figure S3).