A Case of Proliferative Glomerulonephritis with Monoclonal IgG Deposits That Showed Predominantly Membranous Features

In 2004, the novel category of monoclonal IgG deposition disease has been proposed and termed "proliferative glomerulonephritis with monoclonal IgG deposits" (PGNMID). This disease is characterized by membranoproliferative glomerulonephritis and staining for a single light-chain isotype and gamma heavy-chain subclass. A 76-year-old male who had monoclonal gammopathy was referred to our hospital because of proteinuria. The renal biopsy showed diffuse thickening of the glomerular capillary walls with focal mesangial proliferation. On immunofluorescence study, only IgG1 among the four subclasses and lambda light chains were detected mainly in the glomerular capillary walls. From these results, we diagnosed our case as PGNMID showing predominantly membranous features. Almost all pathological findings on light microscopy of PGNMID are membranoproliferative GN or endocapillary proliferative GN, while membranous GN cases are rare. Here, we present the case of PGNMID that showed predominantly membranous features on light microscopy.