Abstract: FR-PO973
Monoclonal Immunoglobulin Deposition Disease (MIDD) or Proliferative Glomerulonephritis with Monoclonal Immunoglobulin Deposits (PGNMID): Which Diagnosis Fits Better?
Session Information
- Pathology and Lab Medicine - 1
October 25, 2024 | Location: Exhibit Hall, Convention Center
Abstract Time: 10:00 AM - 12:00 PM
Category: Pathology and Lab Medicine
- 1800 Pathology and Lab Medicine
Authors
- Liborio, Alexandre Braga, Universidade de Fortaleza, Fortaleza, CE, Brazil
- Linhares, Rafaela Jucá, Hospital Geral de Fortaleza, Fortaleza, Brazil
- Salles, Louise, Hospital Geral de Fortaleza, Fortaleza, Brazil
- Teixeira, André Costa, Centro Universitario Christus, Fortaleza, Brazil
- Barrero, Dulce Maria Sousa, Hospital Geral de Fortaleza, Fortaleza, Brazil
Introduction
MIDD and PGNMID originate from monoclonal immunoglobulin-glomerular deposits. In MIDD, IF shows κ light chain restriction in up to 90% of cases and tubular basement membrane (TBM) involvement in 100% of cases. In PGNMID, LM shows proliferative or MPGN, and IF, by definition, reveals monotypic deposits restricted to the glomeruli (unlike MIDD), with IgG in 90% of cases. We describe a patient with renal-limited disease presenting a PGNMID-compatible clinical course/light microscopy findings but an IF-based diagnosis of MIDD.
Case Description
48-year-old male presented with dialysis-requiring renal failure, hematuria (more than 100 RBC/HPF), proteinuria of 4.6g/24h and hypoalbuminemia. Due to clinical suspicion of RPGN, high-dose corticoid therapy was initiated. Renal biopsy (figure) demonstrated hypercellularity due to leukocytes and duplication of the GBM. Red congo negative. IF was positive only for κ light chains (4+/4) in both the GBM and TBM. Electron microscopy did not show glomeruli but non-organized electron-dense deposits in TBM. Renal response ocurred one month after corticoid therapy (sCr:1.56 mg/dL and proteinuria,177 mg/24h). Corticoid withdrawal was followed by worsening renal function, leading to reintroduction with new response. A κ peak was present in the urine and despite no evidence of multiple myeloma, bortezomib was added.
Discussion
This case has features that prompt us to reconsider the most fitting diagnosis and, in any case, expand our understanding of the spectrum of glomerular involvement by monoclonal deposits. Although the IF findings (κ restriction and deposits in the TBM) and the initial presentation can be compatible with MIDD, the dramatic and rapid glucocorticoid response aligns with the clearance of inflammatory cells, a main feature of PGNMID as the primary pathologic substrate. Patients with MIDD treated with bortezomib had renal remission, but only after several months (PMID: 30578255). Therefore, we suggest that PGNMID is the most appropriate and more informative diagnosis for clinicians' management; alternatively, two concominant diagnosis can be considered