Ans. b (RPGN). (Ref. Robbin, Pathology 8th ed., 545)Rapidly Progressive (Crescentic) Glomerulonephritis# RPGN is a clinical syndrome and not a specific etiologic form of GN.# Clinically, it is characterized by rapid and progressive loss of renal function with features of the nephritic syndrome, often with severe oliguria and (if untreated) death from renal failure within weeks to months.# Regardless of the cause, the histologic picture is characterized by the presence of crescents (crescentic GN).# These are produced in part by proliferation of the parietal epithelial cells of Bowman's capsule in response to injury and in part by infiltration of monocytes and macrophages.Type I (Anti-GBM Antibody)IdiopathicGoodpasture syndromeType II (Immune Complex)IdiopathicPostinfectious/infection relatedSystemic lupus erythematosusHenoch-Schonlein purpura/IgA nephropathyType III (Pauci-Immune) ANC A AssociatedIdiopathicWegener granulomatosisMicroscopic angiitis