Immunoglobulin G4-related disease mimicking acute appendicitis: The first case report from Türkiye.

Immunoglobulin G4-related disease (IgG4-RD) is a fibroinflammatory condition that can present as mass-like lesions mimicking tumors, infections or immune-mediated diseases. Although multiple organs may be involved, appendiceal involvement is extremely rare with only eight cases reported in the literature. Here, we report a case of a 38-year-old male patient who presented with clinical features of acute appendicitis and underwent laparoscopic appendectomy with cecal wedge resection. Intraoperatively, a mass-like lesion was observed. Histopathological examination revealed IgG4-positive plasma cells, non-necrotizing granulomas, submucosal and subserosal fibrosis consistent with IgG4-RD of the appendix. The patient was discharged on postoperative day one without complications and no clinical abnormalities were noted during a postoperative one-year follow-up period. This report describes the first case of appendiceal IgG4-RD reported from Türkiye. Despite its uniqueness, IgG4-RD should be considered in the differential diagnosis of appendiceal pathologies to ensure accurate diagnosis and patient management.