Rapidly progressive glomerulonephritis

Rapidly progressive glomerulonephritis (RPGN) is a syndrome of the kidney that is characterized by a rapid loss of kidney function, (usually a 50% decline in the glomerular filtration rate (GFR) within 3 months) with glomerular crescent formation seen in at least 50% or 75% of glomeruli seen on kidney biopsies. If left untreated, it rapidly progresses into acute kidney failure and death within months. In 50% of cases, RPGN is associated with an underlying disease such as Goodpasture syndrome, systemic lupus erythematosus or granulomatosis with polyangiitis; the remaining cases are idiopathic. Regardless of the underlying cause, RPGN involves severe injury to the kidneys' glomeruli, with many of the glomeruli containing characteristic glomerular crescents (crescent-shaped scars). Most types of RPGN are characterized by severe and rapid loss of kidney function with marked hematuria; red blood cell casts in the urine; and proteinuria sometimes exceeding three grams in twenty-four hours, a range associated with nephrotic syndrome. Some patients also experience hypertension and edema. Severe disease is characterized by pronounced oliguria or anuria, which portends a poor prognosis. It is thought that antineutrophil cytoplasmic antibodies (ANCA) interact with antigens in the cytoplasm of neutrophils to cause an early degranulation, triggering the release of lytic enzymes at the site of injury and leading to the formation of glomerular crescents that consist primarily of parietal epithelial cells from Bowman's capsule and in some cases podocytes. Serum analysis often aids in the diagnosis of a specific underlying disease. The presence of anti-glomerular basement membrane (GBM) antibodies suggests type I RPGN; antinuclear antibodies (ANA) may support a diagnosis of systemic lupus erythematosus and type II RPGN; and type III and idiopathic RPGN are frequently associated with anti-neutrophil cytoplasmic antibodies (ANCA)-positive serum. Impaired kidney function in an individual who has had the condition for fewer than three months is characteristic of RPGN.