Glomerular crescents in renal amyloidosis: An epiphenomenon or distinct pathology?

There have been several reports of cases of renal amyloidosis with glomerul ar crescents. However, it is not clear whether the association is fortuitou s or pathogenic related. The present study analyzed 105 cases of renal amyl oidosis (61 autopsy cases and 44 biopsy cases) and found glomerular crescen ts in 14 (13.3%) cases. Among the 14 cases with crescents, a female predomi nance was noted (male : female, 3 : 11) and rheumatoid arthritis was the mo st common primary disease of amyloidosis. Immunohistochemical analysis demo nstrated amyloid protein of AA type in 12 cases. According to the histologi c classification, there were 11 cases of mesangial nodular type, which was almost exclusively accompanied by AA amyloid deposition. Of note, the incid ence of crescents neither correlated with the extent of amyloid deposition nor the presence of nephrotic syndrome. By contrast, localization of amyloi d deposition was closely related to crescent formation. Moreover, electron microscopic observation displayed rupture of the glomerular basement membra ne at the site of amyloid deposition. Our results indicated that glomerular crescents were more frequently associated with renal amyloidosis than prev iously appreciated. Rupture of the fragile glomerular basement membrane by amyloid deposition, as revealed by immunostaining and electron microscopy, may be the mechanism of crescent formation. We suggest that glomerular cres cents are a distinct pathology associated with renal amyloidosis, not fortu itous conditions.