Proliferative glomerulonephritis with monoclonal immunoglobulin deposits, light chain variant

Proliferative glomerulonephritis with monoclonal immunoglobulin G deposits (PGNMID) is a type of monoclonal immunoglobulin deposition disease characterized by glomerular injury with membranoproliferative pattern and deposition of monoclonal IgG (usually IgG3). Nasr et al. described a case series of PGNMID with light chain deposition only. 

Unlike PGNMID-IgG, the light chain variant (PGNMID-LC) showed only monoclonal light chain deposits. All 17 patients had either underlying monoclonal gammopathy of renal significance (MGRS) or multiple myeloma. This was in contrast to PGNMID-IgG in which more than two-thirds of patients did not have MGRS or B/plasma cell neoplasm. All 6 patients who had anti-plasma cell therapy with complete hematologic response had renal response.

Although PGNMIC-LC is considered a variant of PGNMID-IgG, its hematological underlying is more like light chain deposition disease (LCDD). 

PGNMID-LC show large subendothelial deposits by LM resembling wire loop in lupus nephritis.
PGNMID-IgG usually has small subendothelial deposits best demonstrated by EM (Image from Nasr et al.)

Nasr SH, Larsen CP, Sirac C, et al. Light chain only variant of proliferative glomerulonephritis with monoclonal immunoglobulin deposits is associated with a high detection rate of the pathogenic plasma cell clone. Kidney Int. 2020;97(3):589‐601. doi:10.1016/j.kint.2019.10.025