Polyposis and early cancer in a patient with low penetrant mutations in MSH6 and APC: hereditary colorectal cancer as a polygenic trait.

Hereditary non-polyposis colorectal cancer and familial adenomatus polyposis are autosomal dominant diseases accounting for 5-7% of all colorectal cancer cases. Inheritance of mutations associated with both syndromes in the same individual has, so far, only been observed in a few cases. This report outlines the findings in a proband of a HNPCC family, who presented with colorectal cancer and with multiple adenomas at the age of 18.