Archives of Pathology & Laboratory Medicine
Context: IgG4-related interstitial nephritis (IRIN) can present as either a renal mass or with acute kidney injury (AKI). The goal of this study was to present our 4 IRIN cases with different clinical scenarios.
Design: Over the past 5 years, we identified 4 cases of IRIN. Each case was evaluated.
Results: Case 1 involved a 60-year-old man with a 3-cm kidney mass. The core biopsy revealed storiform fibrosis and increased IgG4-positive plasma cells (>30 per high-power field), thus diagnosed as IRIN. Case 2 involved a 69-year-old man with medical history of polymyalgia rheumatica and low complements who developed AKI (serum creatinine at 2.8 mg/dL). Light microscopy revealed diffuse interstitial nephritis with significant IgG4+ plasma cells (Figure 2.66). Immunofluorescent (IF) staining showed positive IgG staining along tubular basement membranes (TBM) and electron microscopy (EM) showed deposits along TBM, supporting a diagnosis of IRIN. Case 3 involved an 82-year-old woman who had base serum creatinine at 2.02 mg/dL and underwent a total nephrectomy, which showed 2.5-cm yellow mass and features of IRIN microscopically. In case 4, a 62-year-old man with history of lymphoma developed AKI (serum creatinine of 5.29 mg/dL) and the renal biopsy revealed typical IRIN including all features seen in case 2.
Conclusions: A renal biopsy from renal mass may be needed to confirm IRIN and avoid unnecessary surgical intervention. Also, IRIN can be accompanied by other immune disorders. IgG4 staining and IF/EM findings of TBM deposits are all helpful to reach a final diagnosis of IRIN.
Elzieny M, Li W, Kanaan HD, Zhang P. IgG4-related nephritis ranges from kidney mass to acute kidney injury. Arch Pathol Lab Med. 2022 Sep;146(9):e88-e89. doi: 10.5858/arpa.2022-0231-AB.