Among the 64 biallelic MCM9 variant carriers in the 100000 Genomes Project, 3 individuals (4.7%) had CRC, 2 (3.1%) had colonic polyps, 2 (3.1%) had colonic adenomas, 2 (3.1%) had rectal polyps, 3 (4.7%) had hypothyroidism, 5 (7.8%) had breast cancer, and 2 (3.1%) had epilepsy. The gene discussed is MCM9; the disease is rectal hyperplastic polyp.