Polyps are the primary precursor lesions of colorectal cancer (CRC). Patients with large numbers of polyps (polyposis) are relatively rare and most of them can currently be explained by two strong predisposition genes (APC and MUTYH). However, the remaining 20-30% of polyposis patients remains genetically unexplained.

The authors studied 252 genetically unexplained polyposis patients and identified two genetic variants that give a small risk of developing polyposis. In their first-degree relatives we observed a high incidence of CRC, even in the absence of polyposis. Their findings suggest that these family members will benefit from surveillance by colonoscopy. (By Dr Frederik J Hes, http://jmg.bmj.com/content/early/2013/11/19/jmedgenet-2013-102000 )