Table 1. Original World Health Organization (WHO) classification of lupus nephritis (1974)

Class INormal glomeruli (by light microscopy, immunofluorescence, and electron microscopy)
Class IIPurely mesangial disease
    a. Normocellular mesangium by light microscopy but mesangial deposits by immunofluorescence or electron microscopy
    b. Mesangial hypercellularity with mesangial deposits by immunofluorescence or electron microscopy
Class IIIFocal proliferative glomerulonephritis (<50%)
Class IVDiffuse proliferative glomerulonephritis (≥50%)
Class VMembranous glomerulonephritis