Kidney Week

Abstract: SA-PO0698

Fibrillary Glomerulonephritis in a Patient with Concurrent Diabetic Nephropathy and Misleading Serology: Importance of Tissue Diagnosis

Session Information

• Glomerular Diseases: Complement-Mediated Glomerulopathies and Infection-Related GN
  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

• Bidhan, Sourabh, Vanderbilt University, Nashville, Tennessee, United States

Sourabh Bidhan, MD, MBBS

• Dilaver, Ragibe Gulsah, Vanderbilt University, Nashville, Tennessee, United States

Ragibe Gulsah Dilaver, MD

• Paueksakon, Paisit, Vanderbilt University, Nashville, Tennessee, United States

Paisit Paueksakon, MD

• Sanghani, Neil S., Vanderbilt University, Nashville, Tennessee, United States

Neil S. Sanghani, MD

Introduction

Fibrillary glomerulonephritis (FGN) is a rare immune-complex glomerulonephritis defined by DNAJB9-positive randomly arranged fibrils on electron microscopy. Co-occurrence with ANCA positivity, ANA positivity, and a history of diabetes pose significant diagnostic challenges without renal biopsy confirmation.

Case Description

A 55-year-old woman with longstanding diabetes mellitus, hypertension, and an 11-year history of slowly progressive CKD (creatinine 1.0 mg/dL in 2014) presented in February 2025 with worsening renal function (creatinine 2.63 mg/dL), new proteinuria (UPCR 1.21), and hematuria. Serologic workup revealed ANA 1:160, anti-dsDNA (49 IU/mL), MPO-ANCA positivity, normal complement levels, and negative anti-PLA2r antibody. SPEP, UPEP, and serum free light chains did not reveal evidence of a monoclonal gammopathy. Kidney biopsy demonstrated FGN with diffuse DNAJB9 positivity, 3+ polyclonal IgG-dominant mesangial and capillary loop deposits, 2+ C3 staining, and randomly arranged fibrils measuring 25–35 nm on electron microscopy with 80% foot process effacement. No crescents or necrotizing lesions were identified. Concurrent diabetic nephropathy was present on biopsy as well. Significant chronicity was present with 8 of 17 glomeruli globally sclerosed and 40% interstitial fibrosis. Empiric prednisone 40 mg daily was initiated at presentation, followed by rituximab 1g for 2 doses given 15 days apart after biopsy confirmation. Creatinine stabilized at 2.31 mg/dL at nine months and UPCR declined 63% (1.21 to 0.45). Maintenance rituximab 1g every six months was initiated.

Discussion

This case highlights the importance of obtaining a tissue diagnosis when the serologic profile may be misleading. In a patient with longstanding diabetes, proteinuria is commonly attributed to diabetic nephropathy. Biopsy revealed FGN, carrying distinct therapeutic implications unidentifiable on clinical grounds alone. Concurrent diabetic nephropathy further renders proteinuria an unreliable standalone treatment endpoint, reinforcing that biopsy-proven diagnosis must anchor both therapeutic rationale and response monitoring.