Abstract: SA-PO238
Membranoproliferative Glomerulonephritis Due to Monoclonal Gammopathy of Renal Significance: The Value of Pronase-Digestion
Session Information
- Trainee Case Reports - V
October 27, 2018 | Location: Exhibit Hall, San Diego Convention Center
Abstract Time: 10:00 AM - 12:00 PM
Category: Trainee Case Reports
- 1202 Glomerular Diseases: Immunology and Inflammation
Authors
- Moe, Win Win, NYU Winthrop Hospital, Mineola, New York, United States
- Santoriello, Dominick, Columbia University Medical Center, New York, New York, United States
- Drakakis, James, NYU Winthrop Hospital, Mineola, New York, United States
- Masani, Naveed N., NYU Winthrop Hospital, Mineola, New York, United States
Introduction
Membranoproliferative glomerulonephritis (MPGN), a characteristic light microscopic (LM) finding seen on renal biopsy, is further classified based on immunofluorescence (IF) findings. Immune-complex deposition is one cause of MPGN and may be secondary to monoclonal immunoglobulin deposits. IF on pronase digested tissue can aid in revealing masked monoclonal deposits. A wide spectrum of hematologic diseases are associated with kidney deposition of monoclonal immunoglobulin deposits; however in many patients, there is no identifiable hematologic condition and the term monoclonal gammopathy of renal significance (MGRS) has been applied.
Case Description
A 65-year-old male presents with hypertension, weight gain with bilateral lower extremity edema, and subacute kidney injury with creatinine of 1.81 mg/dl (baseline: 0.9 mg/dl). Urinalysis demonstrated 3+ protein, 2+ blood, with protein creatinine ratio of 10.3 g/g and a serum albumin of 2.8 g/dL. Serum immunofixation was positive for IgG-kappa; remainder of paraprotein workup and glomerular serologies, including complement levels, were either normal or negative.
Renal biopsy findings on light microscopy were consistent with an MPGN pattern of injury, subacute, with nodular mesangial sclerosing features; initial IF demonstrated trace to 1+ granular to semi-linear glomerular capillary wall staining for C3 only; repeat IF performed on pronase-digested tissue revealed trace to 1+ granular to semi-linear glomerular capillary wall staining for IgG with trace C3 and trace kappa, and no significant staining for lambda. Electron microscopy did not reveal any evidence of dense deposit disease. These findings support the diagnosis of MPGN with IgG-kappa monoclonal deposits. Subsequently patient underwent bone marrow biopsy and full body PET scan, neither of which demonstrated any evidence of B-cell clonal expansion/population. Given these findings, the patient’s MPGN appears to be secondary to MGRS. Therapy was initiated with oral corticosteroids and Rituxamab.
Discussion
An MPGN pattern of injury represents a diagnostic and therapeutic challenge. Findings on IF are critical to help determine the underlying cause. This case demonstrates MGRS as underlying etiology of MPGN, and the value of IF analysis via pronase-digestion to aid in “unmasking” hidden monoclonal deposits.