If renal biopsy shows distinct crescents, diagnosis is

Ans. a (RPGN) (Ref. Robbins Pathology 7th/ 976, and H-18th/ch. 283)RAPIDLY PROGRESSIVE GLOMERULONEPHRITIS# RPGN is severe glomerular injury with necrosis and GBM breaks and subsequent proliferation of parietal epithelium (crescents).# RPGN may be immune mediated, as when autoantibodies develop to the GBM in anti-GBM antibody disease or when it develops consequent to immune complex deposition; it can also be pauci-immune, associated with antineutrophil cytoplasmic antibodies.# RPGN is defined by 2 criteria:- Presence of epithelial crescents in more than 70% of glomeruli- Occurrence of rapidly progressive renal failure.# End stage disease occurs within months.# Causes of Crescentic Glomerulonephritis# Type I (Anti-GBM Antibody)- Idiopathic- Goodpasture syndrome# Type 11 (Immune Complex)- Idiopathic- Postinfectious/infection related- Systemic lupus erythematosus- Henoch-Schonlein purpura/IgA nephropathy# Type III (Pauci-immune) ANCA Associated- Idiopathic- Wegener granulomatosis- Microscopic angiitisDiseaseMost Frequent clinical presentationPathogenesisLight MicroscopyFluorescence MicroscopyElectronPost strepto- coccal GNAcute nephritisAntibody mediated; circulating or planted antigenDiffuse proliferation; leukocytic infiltrationGranular IgG and C3 in GBM and mesangiumSubepithelial humpsGood pasture syndromeRapidly progressive glomerulo- nephritisAnti-GBM COL4-A3 antigenProliferation; crescentsLinear IgG and C3; fibrin in crescentsNo deposits; GBM disruptions; fibrinIdiopathicRPGNRapidly progressive glomeru- lonephritisAnti-GBM antibodyProliferation; focal necrosis; crescentsLinear IgG and C3No deposits Immune complex Granular IgG or IgA or IgMDeposits may be present In situ antibody- mediated; antigen unknownDiffuse capillary wall thickenningNegative or equivocalNo depositsMembranous glomerulo-pathyNephrotic syndrome Granular IgG and C3; diffuseSubepithelial depositsMinimal change diseaseNephrotic syndromeUnknown, loss of glomerular polyanion; podocyte injuryNormal; lipid in tubulesNegativeLoss of foot process; No depositsFocal segmental glomerulo- nephritisNephrotic syndrome non-nephrotic proteinuriaUnknown, Ablation nephropathy plasma factor (?); podocyte injuryFocal and segmental sclerosis and hyalinosisFocal; IgM and C3Loss of foot processes; epithelial denudationMembrano- proliferative glomerulone- phritis (MPGN)Nephrotic syndrome(1) Immune complex (I) lgG+ C3;Clq+ C4(l) subendothelial deposits Mesangial pro- liferation; basement membrane thickening; splitting Dense deposit disease(MPGN1)Hematuria(II) Autoantibody: alternative alter- native complement pathway (II) C3+lgG; no CLq or C4(II) Dense deposits Chronic renal failure IgA NephropathyRecurrent hematuria or proteilnuriaUnknown; see textFocal proliferative glomerulonephritis; mesangial wideningIgA +/-lgG, IgM, and C3 in mesangiumMesangial and paramesangial dense depositsChronic glomerulo- nephritisChronic renal failureVariableHyalinized glomeruliGranular or negative