Abstract: SA-PO0750
Same Kidney, Two Biopsies: Different Faces of IgG4-Related Kidney Disease
Session Information
- Glomerular Diseases: Lupus Nephritis, Monoclonal Gammopathy-Related Disease, and Transplantation
October 24, 2026 | Location: Exhibit Hall A, Convention Center
Abstract Time: 10:00 AM - 12:00 PM
Category: Glomerular Diseases
- 1402 Glomerular Diseases: Clinical, Outcomes, and Therapeutics
Authors
- Weerasinghe, Sanjeeva Neranjan, Banner - University Medical Center Tucson, Tucson, Arizona, United States
- Kim, Taesoo, Banner - University Medical Center Tucson, Tucson, Arizona, United States
- González Negrete, Elvira, Banner - University Medical Center Tucson, Tucson, Arizona, United States
Introduction
Immunoglobulin G4 (IgG4)-related diseases are systemic inflammatory diseases that can develop asynchronously in multiple organ systems. In the kidney, it commonly presents as tubulointerstitial nephritis, but it may also mimic malignancy and can be associated with membranous nephropathy . Here, we report a case of simultaneous and heterogeneous manifestation of IgG4-RD within the same kidney demonstrated through a combination of focal and non-focal biopsies.
Case Description
A middle-aged man with prior episodes of pancreatitis presented with abdominal pain, early satiety, and jaundice. MRI showed diffuse enlargement of the pancreas compressing the biliary tree. He was diagnosed with autoimmune pancreatitis and treated. Incidentally, MRI also revealed multiple hypo-enhancing mass-like lesions in the left kidney. eGFR was preserved, but urine protein-creatinine ratio was mildly elevated at 549 mg/g. Initial non-focal kidney biopsy demonstrated fine granular glomerular capillary loop staining for IgG, kappa, and lambda, and electron microscopy showed scattered small subepithelial deposits, suggesting early membranous nephropathy. A second, CT-guided focal biopsy targeting hypo-enhancing lesions was performed, which revealed active tubulointerstitial nephritis with lymphoplasmacytic infiltrate and storiform fibrosis. Immunostaining demonstrated a cluster of IgG4-positive plasma cells, confirming IgG4-related kidney disease. Rituximab was added to the steroid taper. Kidney function remained preserved, and subsequent 24-hour urine collection showed undetectable proteinuria.
Discussion
This case was unique because it demonstrated spatial heterogeneity of IgG4 renal disease and helped show the broad phenotypic spectrum of this disease. We demonstrated that biopsy in the localized hypoechogenic regions of the kidney delineated the classic tubulointerstitial nephritis phenotype whereas the biopsy in the other parts of the kidney demonstrated an early membranous nephropathy. Without this second biopsy, we would not be able to ascertain the full expression of this patient’s phenotype.