Correlation of Polyp Number and Family History of Colon Cancer With Germline MYH Mutations

Background & Aims: Affected individuals with biallelic MYH mutations are believed to display multiple adenomatous polyps without evidence of vertical transmission. Our goal was to determine the detection rate of germline MYH mutations in a high-risk gastrointestinal cancer clinic population by using polyp number as a selection criterion. Methods: Patients were screened for the 2 most common MYH mutations: Y165C and G382D. The complete MYH coding region was sequenced in cases with a heterozygous mutation. Results: Among 45 patients with more than 15 adenomatous polyps not diagnosed with familial adenomatous polyposis, 7 (15.6%) had biallelic MYH mutations. When 122 participants from a high-risk gastrointestinal cancer clinic who did not fulfill these criteria were tested, 2 additional patients with biallelic mutations were identified. Both had young-onset colorectal cancer (age,