Infectious agents are the most common inciting antigens associated with immune complex mediated glomerulonephritis. Post-streptococcal glomerulonephritis is the most common form of glomerulonephritis in children and occurs following a skin or pharyngeal infection with Group A beta-hemolytic streptococci.
Post-infectious glomerulonephritis has also been associated with other bacterial, viral, parasitic, rickettsial and fungal infections.
The precise nature of the antigens involved in the formation of the nephritogenic immune complexes is unknown. Streptococcal antigenic substances have been inconsistently detected in glomeruli and circulating immune complexes have been detected in some patients. Since streptococcal antigens do not always cause disease, other mechanisms may be involved, including alterations in IgG or glomerular components making them immunogenic. Antigens derived from infectious agents may bind to glomerular structures and induce development of in situ immune complexes.
A. Morphologic Features
The glomeruli in post-infectious glomerulonephritis show diffuse mesangial proliferation and endocapillary proliferation accompanied by infiltration of neutrophils and mononuclear inflammatory cells. Crescents may also be present .
Immunofluorescence microscopy demonstrates granular deposits of C3 and IgG along the capillary loops and in the mesangium. The capillary loop deposits become less frequent after a few weeks, but the mesangial deposits persist for a longer period.
Ultrastructurally large subepithelial deposits are present which are usually scattered along the basement membrane. Mesangial deposits are also present.
B. Clinical Course
Post-streptococcal glomerulonephritis is primarily a disease of children, 6 to 7 years of age. The onset is usually abrupt, with a latent period of 7 to 21 days beteen infection and the development of nephritis. During epidemics, the clinical attack rate is 10-12%, but subclinical disease occurs four times more frequently than overt idsease. Asymptomatic contacts may have hematuria.
Common initial clinical manifestations of post-streptococcal glomerulonephritis are:
The acute clinical episode of post-streptococcal glomerulonephritis is usually self-limited and complement levels return to normal within 6 weeks. In most patients hematuria disappears by 6 months but proteinuria may persist for two years in a third of patients.
Early antimicrobial therapy in affected individuals and family members may prevent the spread of streptococcal infections. Treatment of established infection does not prevent the development of post-streptococcal glomerulonephritis, but may lessen its severity.
The prognosis for complete recovery is excellent in children, even in patients with the nephrotic syndrome or crescentic disease at presentation.
The prognosis in adults is less favorable, especially when accompanied by initial severe impairment in renal function, persistent proteinuria and the nephrotic syndrome. The development of crescents is more common in adults.
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Last Modified: February 26, 1997