The pathology of primary IgA glomerulonephritis--a renal biopsy study.

Renal biopsies of 44 Chinese patients with primary IgA glomerulonephritis (IgA Gn) were examined by light (LM), electron (EM) and immunofluorescent microscopy (IF). The diagnosis of IgA Gn was based on IF staining showing predominant mesangial IgA deposition in the absence of systemic diseases. With LM, IgA Gn was not essentially different from other idiopathic forms of glomerulonephritis. The glomerular lesions showed features of focal proliferative glomerulonephritis (45.4%), focal sclerosing glomerulonephritis (25%), minimal glomerular lesions (18.2%) and diffuse mesangial proliferative glomerulonephritis (11.4%). Membranous and membrano-proliferative forms were not encountered. The variable LM findings contrasted markedly with the constancy of IF staining. EM revealed lumpy electron dense deposits in the mesangium in all cases which, in the relative absence of subendothelial and subepithelial deposits, might also be helpful in diagnosis.