Glomerulopathy with distinctive fibrillar deposits but lacking glomerular deposition of type III collagen

Abstract

A 62-year-old woman with nephrotic syndrome underwent a renal biopsy. Under light microscopy, the biopsy findings included lobulation and enlargement of glomeruli, occasional thickening of glomerular capillary walls, and narrowing of the capillary lumen by swollen endothelial cells. Congo red staining was negative for amyloid. No significant intraglomerular fibrin deposition was found by phosphotungstic acid hematoxylin staining. Immunofluorescence microscopy showed no deposition of immunoglobulin G, A, or M; no j or k light chains; and no C3 or C1q. Electron microscopy revealed distinctive subendothelial and mesangial fibrillar deposits, mesangial cell interposition, and swelling and vacuolization of endothelial cells resulting in capillary lumen narrowing. Although some curvilinear fibrillar deposits mimicked the bundles of type III collagen fibers seen in collagenofibrotic glomerulopathy, neither glomerular deposition of type III collagen nor elevation of serum procollagen III peptide was noted. This glomerulopathy does not fulfill any known disease entities with non-amyloid non-immunoglobulinderived organized glomerular deposits.

Glucocorticoid-dependent Tubulointerstitial Nephritis with IgM-positive Plasma Cells Presenting with Intracellular Crystalline Inclusions within the Rough Endoplasmic Reticulum

“…In addition, crystalline inclusions in our case showed striated structures that were 6-7 nm in width with a center-to-center distance of 10-13 nm. Some previous reports have described unusual extracellular deposits of crystals that exhibited striated structures (34,35). Crystals in rER also have been reported to exhibit filament or tubular structures with regular periodicity (19,20,22,26,28,30).…”