Diagnostic Considerations
The following four renal syndromes commonly mimic the early stage of acute glomerulonephritis (AGN):
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Anaphylactoid purpura with nephritis
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Chronic glomerulonephritis with an acute exacerbation
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Idiopathic hematuria
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Familial nephritis
Postinfectious glomerulonephritis must be differentiated from the following conditions:
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Immunoglobulin A (IgA) nephritis - The latent period between infection and onset of nephritis is 1-2 days; alternatively, nephritis may be concomitant with upper respiratory tract infection (ie, “synpharyngitic nephritis,” in contrast to the “postpharyngitic nephritis” seen in poststreptococcal glomerulonephritis [PSGN], which occurs 1-3 weeks later).
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Membranoproliferative glomerulonephritis (MPGN), types I and II - This is a chronic disease, but it can manifest with an acute nephritic picture with hypocomplementemia; failure of acute nephritis to resolve should prompt consideration of this possibility.
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Lupus nephritis - Gross hematuria is unusual in lupus nephritis.
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Glomerulonephritis of chronic infection - This can manifest as acute nephritis. Unlike PSGN, in which the infection may have resolved by the time nephritis occurs, patients with nephritis of chronic infection have an active infection at the time nephritis becomes evident. Circulating immune complexes play an important role in the pathogenesis of AGN in these diseases.
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Vasculitis - Nephritis of methicillin-resistant Staphylococcus aureus (MRSA) may be associated with vasculitic lesions of the lower extremities.
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Predominantly nonglomerular diseases - Thrombotic thrombocytopenic purpura (TTP), hemolytic-uremic syndrome (HUS), atheroembolic renal disease, and acute hypersensitivity interstitial nephritis may present with features of acute nephritic syndrome and should be differentiated.
Go to Emergent Management of Acute Glomerulonephritis and Acute Poststreptococcal Glomerulonephritis for complete information on these topics.
Other problems to be considered include the following:
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Bacterial, viral, and fungal etiologies
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Chronic glomerulonephritis
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Idiopathic hematuria
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Irradiation of Wilms tumor
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Trauma
Differential Diagnoses
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Light microscopy (hematoxylin and eosin stain X 25): Photograph showing enlargement of glomerular tuft with marked decrease of urinary space and hypercellularity. The hypercellularity is due to proliferation of endogenous cells and polymorphonuclear leukocyte infiltrate. Photograph courtesy of Madeleine Moussa, MD, FRCPC, Department of Pathology, London Health Sciences Centre, London, Ontario, Canada.
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Light microscopy (periodic acid-Schiff stain X 40): Photograph showing enlargement of glomerular tuft with marked decrease of urinary space and hypercellularity. The hypercellularity is due to proliferation of endogenous cells and polymorphonuclear leukocyte infiltrate. Photograph courtesy of Madeleine Moussa, MD, FRCPC, Department of Pathology, London Health Sciences Centre, London, Ontario, Canada.
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Immunofluorescence (X25): Fine granular deposits of immunoglobulin G (IgG) along the basement membrane and mesangium, with "starry sky" appearance. Photograph courtesy of Madeleine Moussa, MD, FRCPC, Department of Pathology, London Health Sciences Centre, London, Ontario, Canada.
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Ultrastructure (electron microscopy): Photograph showing proliferation of endothelial cells and mesangial cells and leukocyte infiltrate associated with presence of large, subepithelial, electron-dense deposits (ie, "hump") (see arrow). Photograph courtesy of Madeleine Moussa, MD, FRCPC, Department of Pathology, London Health Sciences Centre, London, Ontario, Canada.
