Attenuated Familial Adenomatous Polyposis

Abstract

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.

Figure 1.

EGD identified no atrophy of the gastric mucosa but detected multiple polyps in the fundus and body that were the same color as the background mucosa, some of which were slightly reddish (yellow arrow).

Figure 2.

A biopsy of the reddish lesion revealed dilated fundic glands with no cellular atypia but a slight increase in the density of the glands.

Figure 3.

Colonoscopy identified two small polyps in the transverse colon. Cold snare polypectomy was performed, and both lesions were identified histologically as tubular adenomas.

Figure 4.

Contrast-enhanced computed tomography (CT) showed scattered, elevated masses with soft tissue density in the patient’s back, suggestive of desmoid tumors (yellow arrows).