<prompt> Crescentic glomerulonephritis seen inPSGNMPGNMembranous GNRPGN  <response>: RPGN presents with an acute reduction in renal function resulting in acute renal failure in a few weeks or months. It is characterized by the formation of crescentscrescentic GNoutside the glomerular capillaries extracapillary GN. crescents are formed from the proliferation of parietal epithelial cells lining Bowmans capsule with contribution from visceral epithelial cells and the invading mononuclear cells. The stimulus for crescent formation appears to be the presence of fibrin in the capsular space. From HARSH MOHAN 7th edition, pg no:654 