A 36-year-old man was diagnosed with multiple gastric polyps by esophagogastroduodenoscopy. Subsequent colonoscopy identified two tubular adenomas, and computed tomography revealed subcutaneous tumors. Based on these findings, we suspected that gastric polyposis was associated with the APC gene, either attenuated familial adenomatous polyposis (AFAP) or gastric adenocarcinoma and proximal polyposis of the stomach (GAPPS). A genetic analysis demonstrated that he had a frameshift variant at codon 1928 of APC, suggesting AFAP. In this era of less Helicobacter pylori infection and frequent use of proton pump inhibitors, diagnoses of AFAP and GAPPS should be considered in patients with prominent gastric fundic gland polyposis.
Keywords: APC-associated polyposis; attenuated familial adenomatous polyposis; desmoid tumor; gastric adenocarcinoma and proximal polyposis of the stomach.