Collagenous gastritis, hyperplastic polyp, and intraepithelial duodenal lymphocytosis in a 15-year-old child: An iconographic case report.

RATIONALE: Collagenous gastritis is an uncommon condition initially identified in 1989 by Colletti and Trainer, characterized by a subepithelial collagen band exceeding 10 μm in thickness. Two patient subgroups have been identified: children and young adults exhibiting severe anemia with illness confined to the gastric mucosa and no colonic involvement, and older individuals presenting with watery diarrhea and collagenous gastritis linked to collagenous colitis. A combination of hyperplastic polyps and Marsh I duodenal lymphocytosis has not been fully reported yet. PATIENT CONCERNS: A 15-year-old boy exhibited a prolonged history of fatigue, lethargy, weight reduction, and poor development. He exhibited iron deficiency anemia. Previous oral iron supplementation had been ineffective, necessitating the use of intravenous iron infusions. An endoscopy revealed a nodular, polypoid stomach with small polyps located in the antrum. DIAGNOSES: Biopsies revealed characteristics of collagenous gastritis, characterized by a thickened subepithelial band. A polyp exhibited elongated, architecturally distorted pits with outpouchings, cystic dilation, and papillary formation but without dysplasia. Intraepithelial lymphocytes exceeding 30 per 100 epithelial cells were seen in the small intestine. In our patient, pericryptal fibroblasts, inflammatory cells, and a distinctive subepithelial band made of randomly oriented collagen fibers were shown histologically and ultrastructurally. INTERVENTIONS: The patient was treated with lansoprazole 30 mg twice daily and famotidine 40 mg once daily, as well as oral iron supplementation. OUTCOMES: Clinical improvement was noted, and hemoglobin and ferritin levels were 123 g/L and 9 µg/L, respectively, at 12 months following therapy. LESSONS: In consideration of a colon-rectal cancer diagnosis of his father at the age of 45 years, we carried out a Search Tool for the Retrieval of Interacting Genes/Proteins and Pymol-based Protein Data Bank study and found that interleukin-4 may be the key factor supporting the occurrence of hyperplastic polyps in collagenous gastritis.