Background: Immunoglobulin G4-related disease (IgG4-RD) and antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) have different clinical and pathological features. However, differentiation between these 2 disorders is sometimes difficult.

Objective: To report a case involving a patient with characteristics of both IgG4-RD and AAV.

Methods: Case report with literature review.

Results: We report a case of myeloperoxidase-ANCA-positive otitis media and rhinosinusitis with pathological features of IgG4-RD in a 73-year-old man. The patient was first clinically suspected to have granulomatosis with polyangiitis. All of the main characteristic pathological features of IgG4-RD were present: dense lymphoplasmacytic infiltration, increased numbers of IgG4-positive plasma cells, storiform-type fibrosis, and obliterative phlebitis.

Conclusions: The simultaneous presence of the characteristics of both IgG4-RD and AAV makes diagnosis and treatment difficult.