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Diagnosis: Proliferative endocapillary glomerulonephritis, postinfectious, with mesangial pattern on immunofluorescence

Postinfectious glomerulonephritis (GN) usually presents histologically as a proliferative endocapillary GN, but there is a mesangial pattern known for a long time. This pattern shows predominantly mesangial proliferation (cellular and/or matrix) with predominant or exclusive immune mesangial deposits, as in he present case. This pattern has been associated with resolving GN. In our case, the mesangial immunopathological pattern (IgG and C3) suggest a resolving pattern; even so, on histology we found glomerular segments with endocapillary proliferation indicating that the GN is still active and it is not the complete or characteristic "mesangial pattern of postinfectious GN".

For a definitive diagnosis of postinfectious GN is necessary to demonstrate prior infection. But in daily practice, this is often not possible, however clinical course and characteristic histologic and immunopathologic features are very useful in the diagnosis. If the "humps" can be found (by Masson's trichrome stain or by electron microscopy) the diagnosis is less difficult. In the present case, previous catarrhal symptoms and dysphagia, low serum C3, morphological features on renal biopsy (with exudative glomerular segments), and abscence of features of other diseases, allowed the diagnosis. Two months after the patient was well and clinical and laboratory tests were normal.

Infection-associated glomerulonephritis is rare in adults and its incidence is progressively declining in developed countries; but in underdeveloped countries incidence remains high. In our series from Colombia postinfectious GN represents 9% of biopsied glomerular diseases (24% in children and 4% in adults) (Arias LF, et al. Glomerular diseases in a Hispanic population: review of a regional renal biopsy database. Sao Paulo Med J. 2009;127(3):140-4 [PubMed link] [Free full text]).

In recent reviews, histological characteristics of postinfectious GN showed two distinct patterns of glomerulonephritis: diffuse endocapillary proliferative glomerulonephritis (65%) and focal mesangial proliferative glomerulonephritis (35%); there were no significant differences in the clinical presentation and outcome between the two groups. Subclinical infection with a more protracted course may contribute to the increasing recognition of this resolving GN at the time of renal biopsy. Another possible explanation is that the atypical morphology may be a peculiar pattern of post-staphylococcal glomerulonephritis, which was increasingly identified in postinfectious GN over the past 10 years (Hsieh YP, et al. Comparison of typical endocapillary and atypical mesangial proliferation in postinfectious glomerulonephritis. Ren Fail. 2010;32(1):55-61. [PubMed link]; Wen YK. The spectrum of adult postinfectious glomerulonephritis in the new millennium. Ren Fail. 2009;31(8):676-82. [PubMed link]).

In a series from New York, the mesangial pattern represented 8.1% of postinfectious GN biopsies (Nasr SH, et al. Acute postinfectious glomerulonephritis in the modern era: experience with 86 adults and review of the literature. Medicine (Baltimore). 2008;87(1):21-32. [PubMed link]).

See the chapter Proliferative Endocapillary Glomerulonephritis of our Tutorial.

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Bibliography

• Wen YK, Chen ML. The significance of atypical morphology in the changes of spectrum of postinfectious glomerulonephritis. Clin Nephrol. 2010;73(3):173-9. [PubMed link]
• Hsieh YP, Wen YK, Chen ML. Comparison of typical endocapillary and atypical mesangial proliferation in postinfectious glomerulonephritis. Ren Fail. 2010;32(1):55-61. [PubMed link]
• Wen YK. Clinicopathological study of infection-associated glomerulonephritis in adults. Int Urol Nephrol. 2009;Aug 11. [Epub ahead of print] [PubMed link]
• Wen YK. The spectrum of adult postinfectious glomerulonephritis in the new millennium. Ren Fail. 2009;31(8):676-82. [PubMed link]
• Nasr SH, Markowitz GS, Stokes MB, Said SM, Valeri AM, D'Agati VD. Acute postinfectious glomerulonephritis in the modern era: experience with 86 adults and review of the literature. Medicine (Baltimore). 2008;87(1):21-32. [PubMed link]

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