Rapidly progressive glomerulonephritis

Rapidly progressive glomerulonephritis is a clinical syndrome of kidney-function loss over days to weeks, usually with glomerular inflammation and crescents on biopsy.

Glomerular crescent: A cellular and fibrin-rich lesion occupying Bowman’s space in a severely injured glomerulus. Crescents are the characteristic biopsy finding in many cases of this syndrome.
Glomerulus: A tuft of capillaries in the kidney where blood filtration begins. The defining inflammation in this syndrome is centered on glomeruli.
Anti-glomerular basement membrane disease: An autoimmune disease in which antibodies target the glomerular basement membrane, sometimes also injuring lung capillaries. It is a treatable cause of rapidly progressive glomerulonephritis with a characteristic antibody test.
Immune complex glomerulonephritis: Glomerular inflammation caused by deposition of antigen–antibody complexes in kidney tissue. Immune deposits distinguish this mechanism from pauci-immune forms of crescentic disease.
Glomerular basement membrane: A specialized extracellular matrix layer forming part of the kidney filtration barrier. Damage to this barrier allows blood and inflammatory material to enter Bowman’s space.
Urinalysis: Laboratory examination of urine for cells, protein, chemicals, and other abnormalities. Urine microscopy can reveal blood, casts, and protein associated with glomerular injury.
ANCA-associated vasculitis: A group of small-vessel vasculitides associated with antineutrophil cytoplasmic antibodies. It can cause crescentic glomerular injury, often with few immune deposits on biopsy.
Pauci-immune glomerulonephritis: Necrotizing glomerular inflammation with few or no immunoglobulin deposits on immunofluorescence. This biopsy pattern commonly accompanies ANCA-associated causes of the syndrome.
Bowman’s capsule: A double-walled structure surrounding each glomerular capillary tuft and collecting filtrate. Crescents form within its urinary space after severe glomerular injury.
Red blood cell cast: A cylindrical urinary sediment formed when red blood cells become trapped in kidney tubules. These casts support a glomerular source for hematuria.

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Microscopic polyangiitisBroader topic: It is a common severe presentation when microscopic polyangiitis affects the kidneys.