Sinonasal IgG4‐related sclerosing disease: A rare entity and challenging diagnosis

OBJECTIVES: To describe the rare presentation, imaging and histological findings, and treatments in patients with IgG4‐related disease (IgG4‐RD) and diagnostic pitfalls and difficulties. METHODS: Cases of sinonasal IgG4‐RD were retrieved, and clinicopathological features were reviewed. RESULTS: Seven cases of sinonasal IgG4‐RD were identified over an 11‐year period, including four males and three females, with an age range of 19–66 years (median 58 years). Patients presented with symptoms related to the mass effect of the lesions or the destructive nature of the disease including fullness, swelling, obstruction, and pain. Serum IgG and IgG4 levels, IgG/IgG4 ratios, storiform fibrosis, obliterative phlebitis, and plasma cell infiltration were seen in varying proportions. Bony erosion and tissue inflammation were present in some cases. CONCLUSION: Sinonasal IgG4‐RD is exceedingly rare among other IgG4‐RD and varied in its clinical presentation thus posing as a clinically difficult disease to diagnosis. Proper clinical, pathological, and immunohistopathological analysis is required for accurate diagnosis. Such disease should be considered in all cases of similar presentation to those in this study. Level of Evidence: 4.