Gastric Mucosal Biopsy Revealing Immunoglobulin G4 (IgG4)-Related Disease With Subtle Macroscopic Changes: A Case Report

Immunoglobulin G4 (IgG4)-related disease affects multiple organs throughout the body, including the pancreas, bile ducts, lacrimal glands, salivary glands, lungs, kidneys, retroperitoneum, and lymph nodes; however, reports of gastrointestinal involvement are scarce. We report the case of a 40-year-old Japanese woman who presented with bilateral eyelid edema and enlargement of the submandibular and parotid glands. Upper gastrointestinal endoscopy was performed due to epigastric discomfort. Although the endoscopy revealed minimal mucosal abnormalities, the gastric mucosal biopsy demonstrated marked IgG4-positive plasma cell infiltration. These findings provided sufficient pathological evidence to establish a diagnosis of IgG4‑related disease. The patient was treated with steroid therapy, which was highly effective and resulted in rapid symptom improvement. This case highlights that in patients with gastrointestinal symptoms, a gastric mucosal biopsy is valuable for the definitive diagnosis of IgG4-related disease, even when gross endoscopic findings are limited.