Depiction of the natural history of glomerular crescents

Crescent formation. In early crescent formation, cytokines and growth factors cross the glomerular basement membrane (GBM) to initiate proliferation of the parietal epithelial cells. Small breaks in the GBM occur secondary to injury from oxidants and proteases from neutrophils and macrophages, thus allowing the macrophage to enter Bowman's space, where it can proliferate. Breaks in Bowman's capsule secondary to the periglomerular inflammation also occur, allowing the entrance of more inflammatory cells as well as fibroblasts. The proliferation of parietal and visceral epithelial cells and macrophages is associated with fibrin deposition, slowly choking the glomerular tuft until filtration becomes impossible. In the late stages, the crescent becomes fibrotic and the glomerulus, end stage. Alternatively, in less severe cases, complete restitution of the glomerular tuft can occur.