Histopathological atlas of renal diseases. Membranoproliferative glomerulonephritis

Membranoproliferative glomerulonephritis (MPGN) is histologically characterized by intense glomerular hypercellularity (mainly due to mesangial proliferation) and diffuse thickening of the glomerular basement membrane with the appearance of "double contours". Two distinct histological forms have been identified - Type I MPGN and type II MPGN. Type I MPGN is characterized by the predominant presence of subendothelial deposits, while Type II MPGN presents dense homogenous deposits in the basement membrane. Actually, despite many morphological and clinical similarities, there are enough histological and immunohistological differences to suggest that Type II MPGN is a separate and distinct entity, caused by different pathogenetic and morphogenetic mechanisms. Some researchers have identified a further entity: Type III MPGN, characterized by the concomitant presence of subendothelial and subepithelial deposits, but many authors at present believe that TYPE III MPGN is a morphological variant of Type I MPGN, given their clinical, immunological, and immohistological similarities.