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

Abstract

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.

Figure 1

Light microscopy findings. (a) Periodic acid-Schiff stain (PAS) staining showed focal mesangial proliferation (original magnification ×400). (b) Periodic acid-methenamine silver (PAM) staining showed thickening of glomerular capillary walls (original magnification ×400). (c) Masson trichrome (MT) staining showed red staining in the subepithelial area (original magnification ×400).

Figure 2

Immunofluorescence findings. IgG was strongly positive mainly in the peripheral capillary walls. C3 was also positive in peripheral pattern. In light-chain staining, kappa chain was entirely negative, but lambda chain was positive in the peripheral capillaries (original magnification ×400).

Figure 3

Findings of IgG subclass staining. IgG1 was positive in peripheral granular pattern. On the other hand, IgG2, IgG3, and IgG4 were all negative (original magnification ×400).

Figure 4

Electron microscopic finding. Electron microscopy showed huge electron-dense deposits in subepithelial, intramembranous, and mesangial lesions (original magnification ×3,000).