Systemic AL amyloidosis. Kidney biopsy. A,B. Light microscopy (Congo red staining, original magnification x 400). Congo red-positive glomerular deposits in the mesangium, capillary walls and Bowman’s capsule (A), with typical apple-green birefringence under polarized light (B). C-E. Immunofluorescence (original magnification x 400). Glomerular amyloid deposits positively stained with the anti-lambda conjugate (C), but not with the anti-kappa conjugate (D). E. Glomerular and arteriolar amyloid deposits showing similar strong staining with the anti-lambda conjugate. F. Electron microscopy (original magnification x 8.000). Glomerular subepithelial amyloid deposits organized into randomly arranged fibrils 7 to 10 nm in external diameter. G,H. Immunoelectron microscopy (original magnification, X 30.000). Glomerular amyloid deposits decorated by 10 nm gold-conjugated anti-lambda antibody (G). No staining was observed with gold-conjugated anti-kappa antibody (H).