Focal Glomerular Immune Complex Deposition: Possible Role of Periglomerular Fibrosis/Atubular Glomeruli

Abstract

Consensus exists among renal pathologists that, in biopsies with immune complex glomerulonephritis, even a single glomerulus with open capillary loops may be sufficient for immunofluorescence and/or electron microscopy evaluation because immune complex deposition is a diffuse phenomenon. However, we have encountered renal biopsies with focal absence of immune complexes in glomeruli on either immunofluorescence or electron microscopy examination despite presence of open glomerular capillary loops. To evaluate renal biopsies with focal immune complex deposition and look for any subtle or unusual morphologic changes in the glomeruli (and in the biopsy in general). Native and transplant renal biopsies were reviewed. All biopsies had been triaged and processed according to our routine protocol for light microscopy, immunofluorescence, and electron microscopy examination. Of 2018 renal biopsies from December 2005 to December 2007, we found 10 such biopsies; 5 native and 5 transplant kidney biopsies. We found that the glomeruli with absent immune complex deposits had periglomerular fibrosis with open, albeit, wrinkled appearing capillary loops but no glomerular sclerosis. We hypothesize that these histologic features are indicative of nonfunctional glomeruli and may be associated with disconnection between the Bowman capsule and proximal tubule (atubular glomeruli). These glomeruli may not have effective filtration, despite some degree of circulation through the open capillary loops, and therefore are unable to accumulate immune complex deposits. If biopsies are small and only such glomeruli are available for immunofluorescence or electron microscopy examination, the absence of immune complex deposition in them should be evaluated carefully.