The crescent forming glomerulonephritis is -

RPGN is characterized by the formation of 'crescents' (crescentic GN) outside the glomerular capillaries (extracapillary GN). 'Crescents' are formed from the proliferation of parietal epithelial cells lining Bowman's capsule with contribution from visceral epithelial cells and the invading mononuclear cells. There are some systemic diseases that are characterized by the formation of crescents. Systemic diseases such as Goodpasture's syndrome, SLE, Henoch-Schlein purpura come under type1 RPGN and they are associated with crescent formation. Ref: Textbook of pathology Harsh Mohan 6th edition page no: 667