IgG4-related Disease of the Retroperitoneum Mimics Malignancy: A Case Report and Literature Review

BACKGROUND/AIM: Immunoglobulin G4-related disease (IgG4-RD) is a systemic, immune-mediated condition characterized by fibroinflammatory lesions affecting multiple organs. When localized in the retroperitoneum, it may mimic malignancy and often leads to surgical intervention. We report the case of a 21-year-old male with retroperitoneal IgG4-RD and review the relevant literature, emphasizing the diagnostic challenges and importance of differential diagnosis. PATIENTS AND METHODS: A case report of a 21-year-old man with retroperitoneal IgG4-RD is presented. A literature review was conducted via Scopus, Embase, and Medline through December 2024, selecting studies with immunohistochemically confirmed retroperitoneal IgG4-RD. Data were independently extracted and analyzed using SPSS software. RESULTS: Of 74 articles retrieved, 22 met the inclusion criteria, totaling 23 patients including our case. The mean age was 62 years, with a male predominance (65%). The left ureter was most commonly involved (52%). Frequent symptoms included localized abdominal pain (61%) and hydronephrosis (96%). Imaging often suggested malignancy, leading 74% of patients to undergo surgery. Histopathology confirmed IgG4-RD in all cases, though only 30% showed IgG4 immunohistochemical positivity. CONCLUSION: Retroperitoneal IgG4-RD closely mimics malignancy, posing significant diagnostic challenges. Elevated serum IgG4 levels and tissue biopsy are critical for accurate diagnosis. IgG4-RD should be considered in patients with unexplained retroperitoneal masses to avoid unnecessary surgery and ensure appropriate treatment.