These MMR gene mutation carriers are at substantially increased risk of colorectal cancer (CRC) with an estimated cumulative risk to age 70 years between 40% and 70% depending on the carrier's sex and the MMR gene that is mutated (Chen et al, 2006; Jenkins et al, 2006; Senter et al, 2008; Baglietto et al, 2010). The gene discussed is MRC1; the disease is colorectal carcinoma.