A Rare Presentation of IgG4-Related Disease with Gastric Outlet Obstruction and Lymphadenopathy: A Case Report

<i>Background.</i> IgG4-related disease (IgG4-RD) is a systemic immune-mediated condition characterized by fibro-inflammatory infiltration. It is a rare disease that can affect any organ, with the involvement of the stomach being particularly uncommon. The clinical manifestations of IgG4-RD are highly variable depending on the type and number of organs involved and mirror the symptoms of other conditions. <i>Case presentation.</i> We report a 61-year-old man who presented with symptoms of gastric outlet obstruction and was subsequently diagnosed with IgG4-RD. The patient experienced recurrent vomiting, early satiety, and substantial weight loss. Imaging studies revealed luminal narrowing in the pyloric region, prompting further endoscopic evaluation. Initial endoscopic biopsies were nondiagnostic. Because the patient's clinical symptoms and previous investigations were highly indicative of malignancy, he underwent distal gastrectomy with Roux en Y anastomosis. However, final histopathology revealed lymphoplasmacytic infiltration and dense fibrosis, confirming the diagnosis of IgG4-RD; no malignant cells were noted. The surgery resulted in symptom improvement. <i>Conclusion.</i> This presentation highlights the diagnostic challenges of IgG4-RD with gastric outlet obstruction, emphasizing the significance of a multidisciplinary approach involving clinical, radiological, and histopathological assessments to achieve an accurate diagnosis and develop tailored management strategies.