The digenic inheritance of MSH6 and MUTYH variants. A, The pedigree shows the coinheritance of the monoallelic variants which encode MSH6 p.Thr1100Met and MUTYH p.Tyr179Cys in a family affected by colorectal cancer. All spouses were unrelated and unaffected by cancer. Genotypes: MSH6 p.Thr1100Met (T1100M; blue); MUTYH p.Tyr179Cys (Y179C; green); ‐, wild type. E, whole‐exome sequencing analysis; T, tumor analysis; ?, unknown phenotype; numbers in symbols, number of unaffected relatives merged for clarity; filled symbols, cancer patients; C, colorectal cancer; E, endometrial cancer; O, ovarian cancer; d., age at death; followed by the age at diagnosis or death. B, in vitro mismatch repair (MMR) activity assay shows wild‐type MMR activity of MSH6 p.Thr1100Met, compared to wild‐type MSH6 (p.Gly529Gly) and a pathogenic MSH6 mutant (p.Gly1139Ser). Data are shown as mean ± SEM of three independent experiments [Color figure can be viewed at wileyonlinelibrary.com]