IgG4-Related Disease, a Systemic or Local Disease: This is the Problem

Abstract

Background: Immunoglobulin G4-related disease (IgG4-RD) is a fibroinflammatory condition that forms tumefactive lesions in various organs, presenting with diverse clinical manifestations. Diagnosis of IgG4-RD could be challenging and relies on characteristic histopathological findings and elevated IgG4+ plasma cell counts. Case Presentation: The patient was a 48-year-old woman with diabetes mellitus initially presented with a painless breast mass. Imaging indicated irregular opacities and lymph nodes in the breast. Biopsy results revealed lymphoplasmacytic infiltration with IgG and IgG4 positivity, overall compatible with IG4-related disease. A mass resection was performed, and intraoperative assessment ruled out malignancy. Then, with a 5-month interval of no symptoms, the patient developed a cheek mass, initially misdiagnosed as low-grade spindle cell sarcoma. Subsequently, she underwent partial maxillectomy and further examination and histology confirmed IgG4-RD, meeting all diagnostic criteria. Conclusion: IgG4-RD is a rare, systemic fibroinflammatory condition with potential to mimic neoplastic processes. While IgG4 serum levels can be elevated, they are not a reliable diagnostic criterion. The two main features of IgG-related disease are an elevated number of IgG4-positive plasma cells within the tissue and a characteristic histopathological appearance including a dense lymphoplasmacytic infiltrate, storiform fibrosis, and obliterative phlebitis. Overall, diagnosis is based on the balance of clinical features, histopathology, and serum markers. This case underscores the diagnostic challenges posed by IgG4-RD, often mistaken for malignancies due to its invasive behavior and emphasizes the importance of considering IgG4-RD in differential diagnoses for tumor-like lesions, particularly when affecting multiple organs, to enable timely treatment decisions and prevent unnecessary interventions.