[From gene to disease; MutYH-associated polyposis coli (MAP)]

MutYH-associated polyposis coli (MAP) is an autosomal recessive inherited form of polyposis and colorectal carcinoma associated with germline mutations in the MutYH gene on chromosome I. The MutYH protein is a base excision repair glycosylase which is involved in the repair of damage caused by the oxidation ofa guanine leading to 8-oxo-7,8-dihydroguanine. If the MutYH protein is dysfunctional, G:C --> T:A mutations in the APC-gene give rise to polyposis and in 50-60% of cases also colorectal carcinoma. MutYH polyposis differs from familial adenomatous polyposis coli in its mode of transmission, later age of onset, a less florid form of polyposis, and fewer extra colonic manifestations.