Abstract
IgG4 related disease (IgG4-RD) is a systemic autoimmune disease characterized by tissue invasion with IgG4-producing plasma cells, resulting in tissue dysfunction. IgG4-RD can affect the kidney in various forms, including renal mass, tubulointerstitial disease, and glomerulonephritis. IgG4-RD can mimic other autoimmune diseases and neoplasms, and as such, maintaining a high index of suspicion is the key to timely diagnosis and treatment. In this paper, we present a case of IgG4-RD that presented with pseudotumor and severe renal dysfunction that progressed to end-stage kidney disease (ESKD), associated with a rare finding of renal vein thrombosis (RVT).