Adenoma Development in a Patient with MUTYH-Associated Polyposis (MAP): New Insights into the Natural Course of Polyp Development

Biallelic germ-line mutations in MUTYH have recently been found to predispose for MUTYH-associated polyposis (MAP). Affected patients present with a wide range of clinical phenotypes at the time of diagnosis, but there is little precise information about the natural course of this disease. Fourteen years of colonoscopic surveillance of an MAP patient (compound heterozygous p.Y165C/p.G382D) showed that adenoma development was slow after initial diagnosis of a single colorectal carcinoma at the age of 44, but then the annual number of new adenomas increased substantially in the patient's early fifties. This course of the disease, with a strong subsequent acceleration of polyp development, may explain the wide range of polyp numbers counted in newly diagnosed MAP patients as a result of the time of observation. Therefore, MAP should also be considered in younger patients (35-55 years) with only few adenomas or colorectal cancer. The high frequency of medium and severe dysplasia in the patient's preferential small adenomas suggests accelerated progression from adenoma to carcinoma in MAP, but this observation must be confirmed by further studies.