Gastric duplication cyst causing hypergastrinemia in an infant

Abstract Gastric duplication cysts are rare congenital anomalies, with fewer than 10% occurring in the stomach. We report a 14‐month‐old girl presenting with failure to thrive, recurrent emesis, hematemesis, and severe duodenitis with ulceration. Laboratory evaluation revealed marked hypergastrinemia (1781 pg/mL), and initial imaging was unrevealing. Persistent symptoms prompted repeat imaging, which identified a 3.7 × 5.2 cm gastric duplication cyst causing gastric outlet obstruction. Surgical resection confirmed gastric mucosa within the cyst, and postoperative gastrin levels normalized. This case represents one of very few reports linking gastric duplication cysts to hypergastrinemia, likely due to isolation of functional gastric mucosa within a closed lumen, resulting in excessive gastrin secretion and peptic injury. The case underscores the importance of considering duplication cysts in pediatric patients with poor growth and the utility of repeat imaging when symptoms persist despite negative initial studies.