Fig. 1

Renal biopsy findings in membranous-like glomerulopathy with masked IgG kappa deposits. Immunofluorescence on fresh tissue showed irregular moderate granular staining for IgG (A) along the glomerular capillaries only in limited basement membranes and rare mesangial deposits. Glomeruli revealed positivity for only kappa light chain (B) and not for lambda (C) (A–C direct immunofluorescence on fresh material, original magnification × 400). Serum amyloid P (SAP) demonstrated stronger and more diffuse staining in glomeruli with a similar granular pattern (D, direct immunofluorescence on fresh tissue, original magnification X 400). E Occasional spikes and holes were evident along the glomerular basement membranes by Jones methanamine silver stain (original magnification × 200; scanner Hamamatsu). F Immunohistochemistry on fixed material with anti-human C4d antibody demonstrated strong granular positivity along glomerular capillary walls with a diffuse but irregular distribution and occasional mesangial deposits (original magnification × 200; scanner Hamamatsu). Glomeruli were negative both for PLA2R (G, original magnification × 200; scanner Hamamatsu) and THSD7A (H, original magnification × 200; scanner Hamamatsu). I, J) Electron microscopy demonstrated sparse amorphous subepithelial deposits along the glomerular basement membrane with occasional spikes and rare mesangial deposits (I,J original magnification × 9800. TEM Philips CM10)