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Abstract: FR-PO1080

The Histopathological Spectrum of Monoclonal Gammopathies of Renal Significance: A Single Centre Experience

Session Information

Category: Glomerular Diseases

  • 1203 Glomerular Diseases: Clinical, Outcomes, and Trials

Authors

  • Kousios, Andreas, Imperial College Healthcare NHS Trust , London, United Kingdom
  • Brah, Tara Kaur, Imperial College Healthcare NHS Trust , London, United Kingdom
  • Troy-Barnes, Ethan, Imperial College Healthcare NHS Trust , London, United Kingdom
  • Duncan, Neill D., Imperial College Healthcare NHS Trust , London, United Kingdom
  • Charif, Rawya, Imperial College Healthcare NHS Trust , London, United Kingdom
  • Cook, H. Terence, Imperial College of London, London, United Kingdom
  • Roufosse, Candice A., Imperial College Healthcare NHS Trust, London, United Kingdom
Background

Monoclonal Gammopathy of Renal Significance (MGRS) encompasses renal histopathological entities caused by Monoclonal Immunoglobulins (MIg) in patients who do not meet criteria of symptomatic lymphoma or myeloma (MM). We describe the spectrum of MGRS histopathological diagnoses in the context of the underlying haematological disease in our centre.

Methods

Native renal biopsies performed during 2006-2017 were reviewed. Those with evidence of MIg or light chain in glomeruli, tubules, vessels and/or interstitium were included. C3GN and TMA were excluded.

Results

Out of 4,374 kidney biopsies, MIg-associated lesions were identified in 163 cases (3.7%). After exclusion of symptomatic MM and lymphomas 68 biopsies (1.5%) were consistent with MGRS. Renal histological diagnoses included: AIg amyloidosis (n=28, 41%), Proliferative GN with MIg Deposits(PGNMID) (n=13, 19%), MIg Deposition Disease(MIDD) (n=12, 18%), Light Chain Tubulopathy (n=5, 7%), Type-1 Cryoglobulinaemic GN (n=6, 9%), Intracapillary Monoclonocal IgM without Cryoglobulin (n=2, 3%), Crystal Cryoglobulinaemia (n=1, 1.5%) and Fibrillary Light Chain restricted GN (n=1, 1.5%). Only 24 out of 42 patients in whom Serum Free Light Chain assay was performed had an abnormal ratio. Overall, haematological diagnosis was possible in bone marrow histology (BMAT) or lymph node biopsy in 53 patients. These included: MGRS with less than 10% plasma cells in BMAT (n=30, 56.6%), Smouldering Myeloma (n=17, 32%), lymphoplasmacytic lymphoma/Waldenstrom's macroglobulinaemia (n=2, 3.7%), chronic lymphocytic leukaemia (n=3, 5.6%) and marginal zone lymphoma (n=1, 1.8%). In 8/13 PGNMID and 3/12 MIDD cases a clonal B cell or plasma cell clone was undetectable in BMAT.

Conclusion

MGRS are increasingly recognised since the term introduction in 2012 and this type of renal histopathology is also frequent in Smouldering Myeloma. Renal histopathology must be interpreted in conjunction with the haematological diagnosis to guide treatment decisions. However, current diagnostic methods underperform and consensus diagnostic approaches incorporating renal and haematological histopathology are lacking.