In a non-diabetic patient, with positive IgG, kappa and lambda staining by immunofluorescence, what is your diagnosis?
The biopsy shows mesangial expansion by non-argyrophilic (Silver-negative) material. The main differential diagnoses for this finding are monoclonal immunoglobulin deposition disease (which is usually positive for a single light chain or immunoglobulin heavy chain, although rare cases of heavy and light chain deposition disease exist), and fibrillary glomerulopathy (FGN). The presence of fibrils ultrastructurally and positive DNAJB9 immunohistochemical staining (Figure 2) in this case helps confirm the diagnosis of fibrillary GN.
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