IgG4-related pseudo-tumor of the kidney and multiple organ involvement mimicked malignancy.

Immunoglobulin G4-related disease (IgG4-RD) is an increasingly recognized systemic condition characterized by particular clinical, serologic, and pathologic features that are consistent across a wide range of organ systems. Herein, we present a rare case of IgG4-RD presenting as multiple inflammatory pseudotumors involving the kidney and other organs involvement mimicking urothelial cell carcinoma with liver, lymph node and lung metastasis. The final diagnosis was made based on characteristic histopathological finding and analysis of IgG4 immunostaining that can distinguish from other conditions. Greater awareness of this disease is needed to ensure diagnoses, which can prevent unnecessary surgical intervention.