Immunotactoid Glomerulonephritis Unmasked From C3 Glomerulopathy: A Diagnostic Dilemma in Spectrum of MGRS

Immunotactoid glomerulonephritis (ITGN) is characterized by organized deposits in the form of microtubules on electron microscopy that stain for monoclonal or polyclonal immunoglobulins (Igs) along with complements. Herein, we discuss a 53-year-old male who had membranoproliferative pattern of glomerular injury with only C3 deposits, suggesting diagnoses of C3 glomerulopathy. Electron microscopy showed parallel arranged microtubules measuring 30–50 nm resembling immunotactoid, which was not compatible with the diagnosis. Immunofixation revealed IgG kappa and tested positive for serum cryoglobulins. Antigen unmasking from the paraffin section revealed IgG kappa restriction. Hence, a diagnosis of ITGN was made. After chemotherapy, the patient achieved remission; however, he relapsed later and started chemotherapy again. This report shows the importance of doing paraffin IF in biopsies with only C3 deposits in adult patients and similarities and differences between ITGN and cryoglobulinemic glomerulonephritis.