What histologic pattern is characteristic of membranous nephropathy?

• A. Tubulointerstitial nephritis
• B. Podocyte foot process effacement without immune deposits
• C. Mesangial proliferation with IgA deposition
• D. Subepithelial immune complex deposition with spike and dome

Answer: (D)

Membranous nephropathy is defined by immune complex deposits in the subepithelial space of the glomerular basement membrane. These deposits provoke the surrounding GBM to form projections, so on silver stains you see a distinctive “spike and dome” pattern—spikes of basement membrane between subepithelial deposits. Electron microscopy confirms subepithelial electron-dense immune complexes, and immunofluorescence shows granular IgG and C3 along the GBM. This combination of subepithelial immune deposits with the spike-and-dome appearance is the hallmark of membranous nephropathy.