Table 2.

Differentiating IgA nephropathy and IgA-dominant PIGN

	IgA nephropathy	IgA dominant PIGN
IF	IgA-dominant or codominant staining	IgA-dominant immunoglobulin staining, with codominant or stronger C3 staining
IF pattern	Granular mesangial staining, variable capillary wall staining	Granular to coarse granular mesangial and segmental capillary wall staining
EM	Electron-dense mesangial±subendothelial deposits, rarely subepithelial deposits	Electron-dense and/or smudgy mesangial deposits, often subepithelial “hump”-shaped deposits, often small subendothelial deposits
LM	Segmental or global mesangial hypercellularity ± endocapillary hypercellularity, sometimes focal crescents	Mesangial and endocapillary hypercellularity, intracapillary neutrophils in acute phase, sometimes focal crescents
Serum complement C3 level	Normal	Low or normal
EM, electron microscopy; LM, light microscopy; IF, immunofluorescence; PIGN, postinfectious glomerulonephritis.