Kidney Week

Abstract: SA-PO0786

A Rare Glomerular Deposition Disease Unmasked by Repeat Biopsy

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

• Costa, Gillian, Walter Reed National Military Medical Center, Bethesda, Maryland, United States

Gillian Costa, MD, MS

• Patrick, Steven J., Walter Reed National Military Medical Center, Bethesda, Maryland, United States

Steven J. Patrick, DO

• Malone, Laura, Walter Reed National Military Medical Center, Bethesda, Maryland, United States

Laura Malone, MD

• Howard, Andrew J., Walter Reed National Military Medical Center, Bethesda, Maryland, United States

Andrew J. Howard, MD

Introduction

Fibronectin glomerulopathy (FNG) is a rare autosomal dominant inherited kidney disease that presents with proteinuria, microscopic hematuria, and hypertension (HTN). Diagnosis is primarily by kidney biopsy, specifically electron microscopy with deposits of 12 to 16 nm fibrils in the mesangium and subendothelium. While the exact mechanism of FNG is unclear, mutations in the fibronectin 1 (FN1) gene are suspected to cause the disease. There is no current treatment with progression to end-stage kidney disease (ESKD) usually on the order of 15 to 20 years. We present a case of a relatively young patient found to have a diagnosis of FNG following biopsy for nephrotic range proteinuria.

Case Description

A 37-year-old female with a history of hypertension (HTN), hyperlipidemia (HLD), and pre-eclampsia in 2007 with subsequent non-nephrotic range proteinuria presented to Nephrology clinic for evaluation of new nephrotic range proteinuria. She was referred after surveillance lab work showed a urine albumin level above the upper limit of quantification (>400mg/dL), subsequently quantified at 4315mg/g, which increased from the urine albumin to creatinine ratio (UACR) of 756.10 mg/g three years prior. Serologic workup was unrevealing to include hepatitis B and C, serum and urine protein electrophoresis, kappa/lambda free light chains, anti-nuclear antibody, and complement C3 and C4. Notably, kidney biopsy in 2011 showed deposition of fibrillary material in the mesangium with negative Congo red staining. Repeat biopsy noted mesangial and subendothelial fibrillary deposits between 11 and 21 nm wide. DnaJ heat shock protein family B member 9 (DNAJB9) testing was negative. Mass spectrometry confirmed with diagnosis with abundant spectra corresponding to fibronectin and fibulin-1. FN1 genetic testing is pending. The patient is being treated conservatively with antiproteinuric therapy, and UACR will be followed closely.

Discussion

With nephrotic range proteinuria and fibrillary deposits on kidney biopsy, FNG should be considered. A negative DNAJB9 immunostain rules out fibrillary glomerulonephritis, which presents similarly. Mass spectrometry testing confirms the diagnosis. FNG is rare with no current guidelines for treatment. This case may provide prognostic (biopsy and kidney function stable over 15 years) and therapeutic (typical antiproteinuric therapy as a means to decrease UACR) information.

Acknowledgment

Disclaimer: The views expressed in this abstract are those of the authors and do not necessarily reflect the official policy or position of the Department of War or the United States Government.