1. Poststreptococcal glomerulonephritis is prototypical for acute endocapillary proliferative glomerulonephritis .
2. The incidence of Poststreptococcal glomerulonephritis is decreasing in western countries and is typically sporadic. Epidemics are still seen, though less commonly.
3. Acute PSGN typically affects children between the ages of
2 and 14 years, but
10% of cases are patients older than 40.
4. It is
more common in males and the familial or cohabitant incidence is as high as 40%.
5. Skin and throat infections with particular M types of streptococci (nephritogenic strains) antedate glomerular disease;
M types 47, 49, 55, 2, 60 and 57 are seen following
impetigo and
M types 1,2,3,4, 25,49 and 12 with
pharyngitis .
6. PSGN due to impetigo develops
2-6 weeks after skin infection and
1-3 weeks after streptococcal pharyngitis .
7. The renal biopsy in PSGN demonstrates hypercellularity of mesangial and endothelial cells, glomerular infiltrates of Polymorphonuclear leukocytes,
granular subendothelial immune deposits of IgM, IgG, C3, C4, C5-9 and subepithelial deposits ( which appear as "humps" ) .
8. PSGN is an immune mediated disease involving putative streptococcal antigens, circulating immune complexes and activation of complement in association with cell-mediated injury.
9. Many candidate antigens have been proposed over the years; three such candidates from nephritogenic streptococci are
zymogen, a precursor of exotoxin B;
glyceraldehyde phosphate dehydrogenase, also known as presorbing antigen (PA-Ag); and
streptokinase. All have a biochemical affinity for GBMs, and in this location act as a target for antibodies.
10. The classic picture is an acute nephritic picture with
hematuria, pyuria, red blood cell casts, edema, hypertension and oliguric renal failure, which may be severe enough to appear as
RPGN.
11. Systemic symptoms of
headache, malaise, anorexia and flank pain ( due to swelling of the renal capsule ) are reported in as many as 50% of cases .
12.
5% of children and 20% of adults have proteinuria in the nephrotic range .
13. In the
first week of symptoms, patients will have a
depressed CH50 and decreased levels of C3 and normal levels of C4 .
14. Positive Rheumatoid factor in 30-40 % of patients .15. Cryoglobulins and circulating immune complexes in 60-70 % of patients .16. ANCA against myeloperoxidase in 10 % of patients .
17.
Positive cultures for streptococcal infection are inconsistently present -
(10-70 %) but
increased titers of ASO (30 %), anti-DNAse (70 %), or antihyaluronidase antibodies (40 %) can help confirm the diagnosis .
18. Consequently the diagnosis of PSGN
rarely requires a renal biopsy .
19. A subclinical disease is reported in some series to be four to five times as common as clinical nephritis, and these latter cases are characterized by asymptomatic microscopic hematuria with low serum complement levels.
20.
Antibiotic treatment for streptococcal infection should be given to all patients and their cohabitants.
21.
Treatment is supportive with control of hypertension, edema and dialysis as needed .
22. There is
no role for immunosuppressive therapy even in the setting of crescents .
23.
Recurrent PSGN is rare despite repeated streptococcal infections .
24.
Early death is rare in children but does occur in the elderly .
25. Overall, the prognosis is good, with
permanent renal failure being very uncommon (1-3%), and even less so in children .
26.
Complete resolution of the proteinuria and hematuria in children occurs within 3-6 weeks of the onset of nephritis .
