Table 3.

The Classification of Lupus Nephritis, Including Lupus Podocytopathy, With Associated Clinical Presentation

Class	Biopsy Findings	Clinical Features	Patients Presenting with Nephrotic Syndrome, %
Class I: minimal mesangial LN	No LM abnormalities; isolated mesangial IC deposits on IF and/or EM	Normal urine or microscopic hematuria	0
Class II: mesangial proliferative LN	Mesangial hypercellularity or matrix expansion with mesangial IC deposits on IF and/or EM	Microscopic hematuria and/or low-grade proteinuria	0
Lupus podocytopathy	Normal glomeruli, FSGS, or mesangial proliferation on LM; IC deposits absent or limited to mesangium on IF and/or EM; diffuse and severe foot process effacement on EM	Nephrotic syndrome	>90
Class III: focal LN	<50% of glomeruli on LM display segmental (<50% of glomerular tuft) or global (>50% of glomerular tuft) endocapillary and/or extracapillary proliferation or sclerosis; mesangial and focal subendothelial IC deposits on IF and EM	Nephritic urine sediment and subnephrotic proteinuria	30
Class IV: diffuse LN	≥50% of glomeruli on LM display endocapillary and/or extracapillary proliferation or sclerosis; mesangial and diffuse subendothelial IC deposits on IF and EM	Nephritic and nephrotic syndromes, hypertension, reduced kidney function	50
Class V: membranous LN	Diffuse thickening of the glomerular capillary walls on LM with subepithelial IC deposits on IF and EM with or without mesangial IC deposits	Nephrotic syndrome	80
Class VI: advanced sclerosing LN	>90% of glomeruli on LM are globally sclerosed with no residual activity	Advanced CKD	<10

Abbreviations: EM, electron microscopy; FSGS, focal segmental glomerulosclerosis; IC, immune complex; IF, immunofluorescence microscopy; LM, light microscopy; LN, lupus nephritis.

Adapted from Bomback.¹⁵