Immunopathology of penicillamine-induced glomerular disease.

Four patients with rheumatoid arthritis developed heavy proteinuria after 5 to 12 months of treatment with D-penicillamine. Light microscopy of renal biopsy samples showed minimal glomerular capillary wall thickening and mesangial matrix increase, or no departure from normal. Electron microscopy, however, revealed subepithelial electron-dense deposits, fusion of epithelial cell foot processes, and evidence of mesangial cell hyperactivity. Immunofluorescence microscopy demonstrated granular capillary wall deposits of IgG and C3. The findings were similar to those in early membranous glomerulonephritis, differences being observed however in the results of staining for the early-acting complement components Clq and C4. It is tentatively concluded that complement was activated by the classical pathway.