Monoclonal Membranous Glomerulopathy

Membranous glomerulopathy (MG) is a common cause of nephrotic syndrome that results from the formation of immune complexes along the subepithelial aspect of the glomerular basement membranes. Approximately 1% of membranous cases will show light chain restriction by immunofluorescence. The majority of MG cases with light chain restricted deposits lack a recognizable secondary etiology. However, absence of PLA2R-positivity within glomerular deposits, positive staining for a single IgG subclass and presence of focal proliferation by light microscopy are worrisome histopathologic features that should prompt a thorough clinical workup to exclude the presence of an underlying lymphoproliferative disorder, even in the absence of a recognizable paraprotein.