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Abstract: FR-PO683

Pronase Digestion to the Rescue

Session Information

Category: Glomerular Diseases

  • 1303 Glomerular Diseases: Clinical‚ Outcomes‚ and Trials

Authors

  • Johnson, Matthew Ryan, Rush University Medical Center, Chicago, Illinois, United States
  • Baxi, Pravir V., Rush University Medical Center, Chicago, Illinois, United States
  • Whittier, William Luke, Rush University Medical Center, Chicago, Illinois, United States
  • Korbet, Stephen M., Rush University Medical Center, Chicago, Illinois, United States
Introduction

Pronase digestion of paraffin-embedded kidney biopsy tissue is a valuable salvage technique used when glomeruli are not present on tissue reserved for routine immunofluorescence (IF). An additional advantage for this technique is that it can “unmask” immunoglobulin (Ig) deposits not seen on routine IF which has both diagnostic and treatment implications. Here, we present three cases in which pronase digestion was utilized to in this way to make unanticipated alternate diagnoses.

Case Description

Case 1: A 70-year-old woman with HTN and follicular lymphoma in remission presented with AKI, subnephrotic proteinuria, and hypercalcemia with an IgG lamda on serum and urine immunofixation. Standard biopsy techniques revealed normal glomeruli and interstitial nephritis.
Case 2: A 50-year-old woman with HTN presented with AKI, hematuria, and nephrotic-range proteinuria with an IgG lamda on serum immunofixation. Standard biopsy methods revealed idiopathic MPGN.
Case 3: A 60-year-old man with HTN presented with nephrotic-range proteinuria and serum and urine immunofixation (-) for monoclonal proteins. Standard biopsy techniques revealed idiopathic immune-complex mediated MPGN.
See Table 1 for details of pronase digestion & final diagnosis.

Discussion

MGRS encompasses a wide spectrum of kidney lesions, and a diagnosis is essential in guiding treatment which is directed towards a clonal disorder. In these cases, routine IF failed to provide a tissue diagnosis and pronase digestion was vital in unmasking a paraprotein-related lesion which ultimately led to appropriate treatment. Pronase digestion should be considered in all cases where there is a high index of clinical suspicion for MGRS despite negative routine IF findings to facilitate early recognition and treatment for these patients.

Table 1: Use of Pronase Digestion Unmasks the Diagnoses