Founder mutation versus full sequencing of MYH for increasing clinical sensitivity.

343 Background: MYH-associated polyposis is an autosomal recessive syndrome caused by biallelic mutations in the base excision repair gene MYH. Initial reports indicated that a majority of European biallelic individuals carried two founder mutations, Y165C and G382D. A common MYH analysis strategy involves evaluation of the two founder mutations (FMs) with subsequent full sequencing only if one of the FMs is identified. This study aimed to determine the sensitivity of full MYH sequencing over the strategy described above in a cohort of individuals that has undergone genetic testing by a commercial laboratory. Methods: A retrospective analysis was performed on 1,522 individuals who had clinical MYH testing ordered either independently or in conjunction with APC gene analysis. All patients underwent MYH analysis for Y165C and G382D. Subsequent full gene sequencing was performed for all patients, except for those biallellic for the two FMs. Demographic, personal, and family cancer histories were collected on...