APC-associated polyposis conditions

APC-associated polyposis conditions result from a constitutional heterozygous pathogenic variant in the APC gene. These conditions include three main clinical phenotypes: the familial adenomatous polyposis (FAP), the attenuated FAP (AFAP) and the gastric adenocarcinoma and proximal polyposis of the stomach (GAPPS). This phenotypic variability corresponds to the differences in the location of the pathogenic variant within the APC gene, even though variations among the individuals and within the families with the identical APC pathogenic variant may occur. Colorectal screening should begin from age 10 to 12 years in FAP and in late teens in AFAP, or earlier if there are gastrointestinal symptoms; the timing of surgery and the extent of resection should be determined on the basis of patient's personal history. Esophagogastroduodenoscopy is recommended by age 20-30 years or prior to colon surgery. Data to support screening for other cancers and manifestations associated with FAP are limited. The efficacy of the screening for gastric cancer and of prophylactic gastrectomy for patients with GAPPS is currently unknown.