Congophilic fibrils in the glomeruli with polyclonal immunoglobulin gamma staining - another cause for diagnostic overlap: A case report

Figure 1 Direct immunofluorescence on frozen tissue along with electron microscopy. A-C: Immunoglobulin gamma (IgG), kappa and lambda, smudgy predominantly mesangial staining; D: Ultrastructural examination shows randomly arranged fibrils in the glomeruli, measuring 10 nm in mean diameter (uranyl acetate lead citrate fixation); E-H: Direct immunofluorescence (DIF) for IgG subclasses demonstrated predominantly IgG1 but also mild to moderate IgG2 and IgG4, appears polytypic. IgG3 is negative (DIF images 40 ×).

Figure 2 Mass spectrometry protein identification report (“scaffold”) shows presence of proteins deposited with amyloid of all types including serum amyloid P component, apolipoprotein A4 and apolipoprotein E; thereby confirming the diagnosis of amyloidosis. In addition, it also shows high peptide counts for IgG heavy chain and lambda light chain, but kappa light chains are seen as well.