Renal involvement patterns of amyloid nephropathy: a comparison with diabetic nephropathy

Thirty kidney specimens obtained from 26 patients with intrarenal amyloid deposition were evaluated. The deposited amyloid belonged to AL protein in 15 cases and AA protein in 11. The intrarenal distribution was examined. Intraglomerular nodular pattern showed a wider extraglomerular distribution of amyloid with a florid accumulation along the vasa recta in the outer medulla, whereas intraglomerular diffuse pattern had amyloid deposition confined mainly to a narrow range surrounding the glomeruli. However, no essential difference was appreciated between AL and AA proteins in the intrarenal distribution, although the former more often disclosed the diffuse pattern. There were many morphological expressions resembling diabetic nephropathy; in addition to the diffuse and nodular pictures, capsular drop-like deposits along Bowman's capsule, simultaneous deposition in the afferent and efferent arterioles, glomerular microaneurysm of early stage, and accumulation along the tubular basement membrane were observed in amyloid nephropathy. Thus, the spicule formation in renal amyloidosis and the diffuse thickening of glomerular and tubular basement membranes in the diabetic emerged as the respective specific lesion. The implicated pathogenesis of diabetic nephropathy was also discussed.