Based on IF findings, a more pathogenic reclassification of MPGN has been proposed into the following three subtypes (1): (i) Ig-associated MPGN, (ii) MPGN with dominant C3, and (iii) idiopathic MPGN (not C3G or Ig associated). The gene discussed is C3; the disease is primary membranoproliferative glomerulonephritis.