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Kidney Week

Abstract: PO1858

Use of Pronase-Treated Paraffin Immunofluorescence to Unmask a Reclusive Glomerular Disease

Session Information

Category: Glomerular Diseases

  • 1203 Glomerular Diseases: Clinical, Outcomes, and Trials

Authors

  • Truong, Phuong, Dallas Renal Group, Dallas, Texas, United States
  • Ilahe, Amna, Dallas Renal Group, Dallas, Texas, United States
  • Nadella, Rama, Dallas Renal Group, Dallas, Texas, United States
  • Mahbod, Diana, Dallas Renal Group, Dallas, Texas, United States
  • Larsen, Christopher Patrick, Arkana Laboratories, Little Rock, Arkansas, United States
  • Agha, Irfan, Dallas Renal Group, Dallas, Texas, United States
Introduction

Interpretation of renal biopsy depends on light, IF and electron microscopy. Direct IF on unfixed frozen tissue sometimes fails to pick up immunoglobulins. Treatment of paraffin embedded formalin-fixed tissue with pronase renders such Igs more amenable to detection.

We present a case of a young woman where use of this "unmasking" technique allowed the correct diagnosis to be made.

Case Description

A 24 YO WF presented to our GN Clinic with intermittent edema, proteinuria and hematuria noticed about a year ago. Her creatinine was 1.5 mg/dl. Urine Pr/Cr ratio was 1.8 g/g. Her ANA was 1:320 but the rest of the antibody panel was negative. C3 and C4 were normal. Lupus Anticoagulant, beta 2 GPI, anticardiolipin IgG and IgM were positive.
Screens for paraproteins and relevant viruses were negative.

Renal Biopsy: 20/31 glomeruli were globally sclerotic. Intact glomeruli showed mesangial proliferation and hypercellularity. IF showed C3+ but all other stains were negative.
IF on pronase digested, paraffin embedded tissue stained IgG, C3 and kappa with no lambda. Stain for SAP was positive.
EM showed numerous mesangial deposits, some sub-epithelial but no sub-endothelial deposits.

Based on above, she was diagnosed with Membranous like glomerulopathy with masked IgG-kappa deposits. Her age, race, gender, Ab profile as well as biopsy findings all supported the diagnosis. She was started on immunosuppression therapy to attempt salvage of renal function and delay progression.

Discussion

Refinement in IF techniques has expanded our diagnostic ability and mechanistic understanding of glomerular disease.
Use of paraffin embedded tissue for IF after pronase treatment helps discover Ig deposits not picked up by traditional IF. This can prove critical in correctly diagnosing glomerular disease, as exemplified in this case.
This patient could have been misdiagnosed as C3 glomerulopathy based on traditional IF. Unmasking IgG-kappa deposits allowed us to correctly diagnose her with a rare disease, MGMID.
This technique expands our ability to correctly diagnose glomerular disease and should be applied routinely.

IF on Paraffin Embedded Tissue