Table 1.

Classification of lupus nephritis

Class	WHO (1982)	ISN/RPSb (2003)
I	Normal glomeruli Nil by all techniques Normal LM, deposits by EM/IF	Minimal mesangial Normal LM. Deposits by IF ± EM. No longer includes those with normal IF/EM
II	Pure mesangial Mesangial widening or hypercellularity Moderate hypercellularity	Mesangial proliferative
III	Focal segmentala ‘Active’ necrotizing lesions ‘Active’ and sclerosing lesions Sclerosing lesions	Focal (<50% glomeruli)c A. Active lesions A/C. Active and chronic lesions C. Chronic inactive lesions with scars
IV	Diffusea Without segmental lesions ‘Active’ necrotizing lesions ‘Active’ and sclerosing lesions Sclerosing lesions	Diffuse segmental (IV-S) or global (IV-G)d (≥50% glomeruli segmental or global lesions). A, A/C, C as above
V	Diffuse membranous Pure membranous Assoc class IIa/b lesions Assoc class IIIa-c lesions Assoc class IVa-d lesions	Membranous May occur in combination with class III or IV, in which case both will be diagnosed
VI	Advanced sclerosinga	Advanced sclerosing (≥90% of glomeruli globally sclerosed without residual activity)

Notes:

^aPercentage was not stipulated in the 1982 modification of the WHO criteria;

^bIndicate and grade (mild, moderate, severe) tubular atrophy, interstitial inflammation and fibrosis, severity of arteriosclerosis or other vascular lesions;

^cIndicate the proportion of glomeruli with active and with sclerotic lesions;

^dIndicate the proportion of glomeruli with fibrinoid necrosis and cellular crescents.

Abbreviations: EM, electron microscopy; IF, immunofluorescence; ISN/RPS, International Society of Nephrology/Renal Pathology Society; LM, light microscopy; WHO, World Health Organization.