Proliferative glomerulonephritis with monoclonal immunoglobulin deposition disease: The utility of routine staining with immunoglobulin light chains.

Proliferative glomerulonephritis occurring as a consequence of monoclonal glomerular deposits of IgG is uncommon. It is a form of renal involvement in monoclonal gammopathy that mimics immune complex glomerulonephritis. Here, we report the first series of proliferative glomerulonephritis with monoclonal IgG deposits (PGNMID) from the Indian subcontinent highlighting use of light chain immunofluorescence (IF) in routine renal biopsy interpretation. We retrieved 6 patients diagnosed as proliferative glomerulonephritis with monoclonal IgG deposits (PGNMID) out of 160 biopsies (3.7%) with membranoproliferative patterns over 5 1/2 years (2009-2014), one of whom had recurrence 6 months post-renal transplant. Four (67%) patients presented with rapidly progressive renal failure and two (33%) with nephrotic syndrome. None of these patients had overt multiple myeloma. The predominant histologic pattern was membranoproliferative with all the biopsies showing IgG3 Kappa deposits on IF. The deposits were primarily subendothelial on electron microscopy.

Light chain proximal tubulopathy with cast nephropathy in a case of multiple myeloma.

The renal diseases most frequently associated with myeloma include cast nephropathy (CN), amyloidosis and monoclonal immunoglobulin deposition disease. Light chain proximal tubulopathy (LCPT) is reported less frequently. Majority of the cases with κ-restriction present with Fanconi syndrome (FS) and show crystals in proximal tubular epithelial cytoplasm. In contrast, those with λ-restriction are infrequently associated with FS and show cytoplasmic vacuolations in proximal tubular epithelial cytoplasm. Combination of morphologies in kidney affected by plasma cell dyscrasias is rare and co-existence of LCPT and CN is one of the rarest. We report a case of multiple myeloma having this rare combination of morphologies.

Monoclonal gammopathy associated membranous glomerulonephritis: A rare entity.

A 40-year-old male presented with nephrotic syndrome. Light microscopic analysis of the renal biopsy showed thickening of the glomerular capillary wall. Immunofluorescence examination revealed granular deposition of monoclonal immunoglobulin (Ig) G3-kappa and complement C3 along the glomerular basement membrane. Electron microscopy showed subepithelial electron dense deposits, thus confirming membranous glomerulonephritis (MGN) with monoclonal gammopathy. MGN with monoclonal gammopathy is an extremely rare but distinctive entity. This patient was treated with a combination of bortezomib, thalidomide and dexamethasone and showed partial remission of his nephrotic state and dysproteinemia.