Spicular arrangement of amyloid in renal biopsy

Abstract

A spicular arrangement of amyloid on the epithelial aspect of the glomerular basement membrane has been seen to a variable degree in silver-stained sections of renal biopsies in eight of 38 patients with amyloidosis. Electron microscopical examination revealed a spectrum of appearances of the amyloid fibrils which would account for this finding. Only two of these eight patients had amyloidosis secondary to chronic infection, a much lower proportion than in the group as a whole. The possibility of confusion with membranous nephropathy is discussed with relevance to possible modes of treatment.

Perimembranous-Type Renal Amyloidosis: A Peculiar Form of AL Amyloidosis

“…Although no specific typing of amyloid deposits was offered, cases reported by Ansell and Joekes [7], and by Moorthy and Burkholder [8] probably be longed to primary amyloidosis, which has been shown to be AL amyloidosis in nature [15]: their glomerular mor phology was highly similar to ours. It is therefore our opinion that perimembranous-type renal amyloidosis is a specific form of AL amyloidosis in which the capillary loops are particularly susceptible to amyloid deposits.…”

“…This type of amyl oidosis principally involved the subepithelial aspect of the glomerular capillary wall. Similar cases of renal amyl oidosis have been reported by Ansell and Joekes [7], followed by Moorthy and Burkholder [8]. As one of the most representative features, this type of amyloidosis invariably exhibited a spicular formation, which, in typi cal cases, mimicked the histopathological picture of membranous glomerulonephritis (MGN) [6][7][8].…”

“…In morphology, amyloid deposits were present predomi nantly in the epithelial side of the capillary wall often showing a florid spicular formation, which, particularly in the early stage, resembled the spikes in MGN [6][7][8]. In contrast, involvement of the mesangium and subendothelial side of the capillary wall was inconspicuous.…”

“…Finally, one must bear in mind that at its early stage one is liable to overlook perimembranous-type renal amyloidosis on routine light microscopy and that spi cules made visible with silver staining often resemble the spikes of MGN [2,[6][7][8]20]. The discrimination between them hardly presents a problem [20]: MGN spikes on silver-stained sections are uniform in lenght and involve all capillaries and glomeruli to a roughly equal extent; similarly stained spicules vary in length, tend to distri bute themselves somewhat scatteredly and are often asso ciated with a decreased argylrophilia of the subjacent GBM.…”

“…A spicular formation, which was defined as argyrophilic perpendicular projec tions on the epithelial side of the GBM [7], was invariably associated with it and often exuberant. In contrast, in volvement of the mesangium and endothelial side of the capillary wall was inconspicuous.…”