Gold nephropathy prototype of membranous glomerulonephritis.

In 7 of 10 kidney biopsies from patients with seronegative rheumatoid arthritis who had developed proteinuria during treatment with gold, electron microscopy showed changes typical of membranous glomerulonephritis. When the disease was of short duration, the only lesions seen were subepithelial deposits. The deposits were often located between intact epithelial foot processes and were demarcated externally by the slit membranes. In disease of longer duration, basement membrane changes occurred; these included projections and a layer of basement membrane over the deposits. The findings indicate that subepithelial deposits are primarily formed between intact foot processes, which would explain their unique discrete character (the basis of the typical granular immunofluorescent staining pattern of immune complex glomerulonephritis). The secondary basement membrane changes seem to evolve according to a constant pattern. The evolutionary process, probably signifying a healing process, is believed to be governed primarily by a synthesis of basement membrane performed by the epithelial cells.