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# Lupus nephritis

- Lesion

Immune complexes in systemic lupus lodge in the glomeruli; where and how much they lodge sets the class and the treatment.

Updated Nov 12, 2026

## Key points

- Class I minimal mesangial, II mesangial proliferative, III focal (

## What it is

Kidney disease affects about half of patients with systemic lupus and is a main driver of its outcome. Complexes of nuclear antigens (DNA, nucleosomes) and antibodies deposit in the mesangium, under the endothelium or under the podocyte, and the pattern is graded in six classes. Diffuse proliferative disease (class IV) is the commonest and most severe active form. Lupus also damages the kidney through thrombotic microangiopathy (antiphospholipid antibodies) and tubulointerstitial inflammation.

## Structure

- Active lesions: endocapillary proliferation, karyorrhexis, fibrinoid necrosis, wire loops, hyaline thrombi and crescents.
- Chronic lesions: glomerular sclerosis, fibrous crescents, tubular atrophy and interstitial fibrosis.
- Interstitial inflammation and deposits along tubular basement membranes are common.
- The biopsy report gives the class and indices of activity and chronicity.

## Lupus nephritis classes (simplified)

| Class | Main lesion | Usual presentation |
| --- | --- | --- |
| I | Mesangial deposits, normal LM | Little or none |
| II | Mesangial proliferation | Mild hematuria or proteinuria |
| III | Focal proliferation, under half of glomeruli | Hematuria, proteinuria |
| IV | Diffuse proliferation, wire loops, crescents | Nephritic and nephrotic, hypertension, falling GFR |
| [V](https://durgical.com/en/conditions/membranous-nephropathy/) | Membranous (subepithelial deposits) | Nephrotic syndrome |
| VI | Over nine in ten glomeruli sclerosed | Chronic kidney disease |

## Clinical notes

- Active urinary sediment, low C3 and C4 and rising anti-dsDNA suggest active proliferative nephritis.
- Lupus is frequent in young women in Latin America, and nephritis is often more severe in Hispanic patients.

## Memory aid

One to six, from the mesangium to the scar: IV is the fire, V is the leak, VI is the ash.

## Test yourself

Think of the answer, then tap the question to see it.

## Which lupus class is the commonest and most severe active form?

Class IV, diffuse proliferative lupus nephritis.

## What are wire loops?

Capillary walls thickened by large subendothelial immune deposits, seen as rigid eosinophilic loops on light microscopy.

## What does full-house immunofluorescence mean?

Staining for IgG, IgA, IgM, C3 and C1q together, typical of lupus nephritis.

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## Elsewhere in DurgiPedia

- [Type III hypersensitivity (immune complexes)](https://durgical.com/en/immunology/type-iii-hypersensitivity/)
- [Immunofluorescence and the ANA test](https://durgical.com/en/immunology/immunofluorescence-and-the-ana-test/)

## Connections

## Related 4

- [Immune mechanisms of glomerular injury](https://durgical.com/en/general-pathology/immune-mechanisms-of-glomerular-injury/)
- [Membranous nephropathy: PLA2R, subepithelial deposits and spikes](https://durgical.com/en/general-pathology/membranous-nephropathy-pla2r-subepithelial-deposits-and-spikes/)
- [Thrombotic microangiopathy: the kidney](https://durgical.com/en/general-pathology/thrombotic-microangiopathy-the-kidney/)
- [Crescentic (rapidly progressive) glomerulonephritis](https://durgical.com/en/general-pathology/crescentic-glomerulonephritis/)

## Related conditions 4

- [Lupus nephritis](https://durgical.com/en/conditions/lupus-nephritis/)
- [Systemic lupus erythematosus](https://durgical.com/en/conditions/systemic-lupus-erythematosus/)
- [Antiphospholipid syndrome](https://durgical.com/en/conditions/antiphospholipid-syndrome/)
- [Nephrotic syndrome](https://durgical.com/en/conditions/nephrotic-syndrome/)

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Educational content on the mechanisms of disease; not a diagnostic or treatment guide and no substitute for a health professional's advice. No doses are given.

Sources: [Lupus nephritis: MedlinePlus Medical Encyclopedia](https://medlineplus.gov/ency/article/000481.htm) (MedlinePlus, US National Library of Medicine, 2025).

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Representative model, for educational purposes only.

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Source: https://durgical.com/en/general-pathology/lupus-nephritis/
License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/general-pathology/lupus-nephritis/