A case of attenuated familial adenomatous polyposis coli (AFAP)

We describe an asymptomatic female patient who was diagnosed with multiple tubular and tubulovillous adenomas in the right-sided colon on routine colonoscopy at the age of 59 years. Genetic testing identified a germline truncating mutation at codon 405 (R405X) of the adenomatous polyposis coli (APC) gene. This mutation is located in the alternatively spliced region of exon 9, a region that is associated with an attenuated phenotype of familial adenomatous polyposis (AFAP). To our knowledge this report describes for the first time the R405X germline mutation in association with AFAP. Our patient had no extracolonic manifestations of AFAP. Treatment consisted of a right hemicolectomy with ileotransversal anastomosis plus complete endoscopic polypectomy in the left-sided colon. AFAP is a poorly defined condition with unknown prevalence and penetrance that requires individual therapy and life-long surveillance. Because of marked intrafamilial phenotypic variance, it is crucial to identify these patients and implement proper endoscopic surveillance at an early age in family members carrying this mutation.