Kidney Week

Abstract: TH-PO720

Factor B: The "It" Factor in Infection-Related Glomerulonephritis

Session Information

• Glomerular Diseases: Case Reports - 1
  October 24, 2024 | Location: Exhibit Hall, Convention Center
  Abstract Time: 10:00 AM - 12:00 PM

Category: Glomerular Diseases

• 1402 Glomerular Diseases: Clinical, Outcomes, and Therapeutics

Authors

• Grigsby, Jennifer L., University of Nebraska Medical Center Department of Internal Medicine, Omaha, Nebraska, United States

Jennifer L. Grigsby, MD

• Magliulo, Eric, University of Nebraska Medical Center Department of Internal Medicine, Omaha, Nebraska, United States

Eric Magliulo, MD

• Mcmillan, David A., University of Nebraska Medical Center Department of Internal Medicine, Omaha, Nebraska, United States

David A. Mcmillan, DO

• Foster, Kirk W., University of Nebraska Medical Center Department of Pathology and Microbiology, Omaha, Nebraska, United States

Kirk W. Foster, MD

• Ravipati, Prasanth, University of Nebraska Medical Center Department of Internal Medicine, Omaha, Nebraska, United States

Prasanth Ravipati, MD

Introduction

Infection-Related Glomerulonephritis (IRGN) and C3 Glomerulopathy (C3G) demonstrate considerable clinicopathologic overlap, presenting a diagnostic challenge to clinicians and making selection of an appropriate treatment regimen difficult. We present a case of IRGN which highlights this diagnostic conundrum.

Case Description

A 43-year-old man presented with volume overload, acute kidney injury, 2 grams of proteinuria, and hypocomplementemia without a history or clinical signs of recent infection. Kidney biopsy demonstrated proliferative glomerulonephritis with immune complex deposition with co-dominant staining of C3 and IgG by immunofluorescence. These findings appeared most consistent with a diagnosis of IRGN; however, with primarily subendothelial and mesangial deposits on electron microscopy, lack of infectious history, and a family history notable for chronic kidney disease in multiple relatives, there was concern for familial hypocomplementemia or C3G. His renal function continued to worsen, requiring intermittent hemodialysis and initiation of empiric pulse solumedrol followed by daily prednisone and mycophenolate mofetil. After being discharged, autoantibody testing returned positive for Factor B autoantibodies. Genetic testing otherwise was negative. Given the previously described strong association of Factor B autoantibodies and IRGN, immune suppression was discontinued. Ten weeks after his initial presentation, repeat labs demonstrated resolution of his hypocomplementemia, near resolution of his proteinuria, and return of serum creatinine to normal (0.9 mg/dL).

Discussion

This patient was ultimately diagnosed with IRGN; however, features of his presentation raised concern for C3G. Factor B autoantibodies have been shown to contribute to transient dysregulation of the alternative complement pathway and have been found in a significantly higher proportion of patients with IRGN compared to C3G. This case highlights the utility of diagnostic complement testing, as the positive Factor B autoantibody helped inform the decision to discontinue immune suppression and limit potential related toxicities. Improvement in timeliness and availability of complement testing is needed to aid clinicians faced with diagnostic uncertainty in the realm of C3G.