Lupus Nephritis

The contract between this chapter and the reader.

1. 1. Define lupus nephritis as the systemic immune-complex GN.
2. 2. Explain the mechanism and the ‘full-house’ immunofluorescence.
3. 3. Recognise the clinical and serologic features.
4. 4. Apply the ISN/RPS classification (classes I–VI).
5. 5. Identify the proliferative classes needing aggressive treatment.
6. 6. Induce proliferative lupus nephritis (steroids + mycophenolate/cyclophosphamide).
7. 7. Use newer agents (belimumab, voclosporin) and maintenance.
8. 8. Manage membranous (class V) lupus.
9. 9. Monitor activity and understand the prognosis.

A sixty-second reading. Each bullet stands alone.

• Lupus nephritis is the renal involvement of systemic lupus, an immune-complex glomerulonephritis.
• Immune complexes (with anti-dsDNA) deposit and activate the classical complement pathway, lowering C3 and C4.
• Immunofluorescence shows a characteristic “full-house” pattern (IgG, IgA, IgM, C3, C1q).
• It is classified by the ISN/RPS system into classes I to VI.
• The proliferative classes (III and IV) are the most severe and need aggressive immunosuppression.
• Class V is membranous lupus, presenting nephrotic, and can coexist with proliferative disease.
• Biopsy is essential to class the disease and guide treatment.
• Proliferative lupus nephritis is induced with corticosteroids plus mycophenolate or cyclophosphamide.
• Newer agents (belimumab, voclosporin) are added to standard therapy for better renal response.
• Maintenance is mycophenolate or azathioprine for years, with steroid tapering.
• Hydroxychloroquine is given to all lupus patients to reduce flares.
• Anti-dsDNA and complement track renal activity.
• Untreated proliferative lupus nephritis carries a significant risk of kidney failure.

The medical core. An expert should agree lupus nephritis is fully covered here.

Why it matters at the bedside

Lupus nephritis is where systemic lupus becomes an organ-threatening kidney disease, and it is one of the main determinants of how patients with lupus do. It is also the disease that most rewards a disciplined approach: biopsy to class it, treat the class, give everyone hydroxychloroquine, and follow the antibody and complement. Get the class right and the treatment follows.

What it is and the mechanism

• Lupus nephritis is the renal manifestation of systemic lupus erythematosus — the prototypic systemic immune-complex glomerulonephritis. Autoantibodies (notably anti-double-stranded-DNA) and immune complexes deposit in the glomerulus and activate complement, driving inflammation. It is the systemic autoimmune disease made renal, and it can take almost any glomerular form depending on where and how the complexes deposit.

Full-house immunofluorescence and complement

• Two laboratory signatures are characteristic. On the biopsy, immunofluorescence shows a ‘full-house’ pattern — staining for IgG, IgA, IgM, C3, and C1q together — reflecting the polyclonal immune-complex deposition. And in the blood, the classical complement pathway is consumed, so both C3 and C4 are low (the low-C3-and-low-C4 pattern of the complement chapter), which both supports the diagnosis and tracks activity.

Clinical and serologic features

• Lupus nephritis occurs in a large fraction of lupus patients and is a major driver of morbidity and mortality. Its presentation varies enormously by class — from asymptomatic urinary abnormalities to nephrotic, nephritic, or rapidly progressive disease — usually alongside systemic lupus features (rash, arthritis, serositis, cytopenias). The serology — a positive ANA, anti-dsDNA (which correlates with renal activity), and low complement — frames the diagnosis.

The ISN/RPS classification

• Lupus nephritis is classified by the ISN/RPS system into six classes: I (minimal mesangial), II (mesangial proliferative), III (focal proliferative, under half the glomeruli), IV (diffuse proliferative, half or more — the most severe and common needing treatment), V (membranous), and VI (advanced sclerosing). Each lesion is also graded for active versus chronic features. Because the class dictates the treatment, the biopsy is essential.

The proliferative classes

• Classes III and IV — focal and diffuse proliferative — are the aggressive, organ-threatening forms, with endocapillary proliferation and active inflammation that, untreated, carry a real risk of kidney failure. They are the classes that require aggressive immunosuppression, and class IV in particular is both the most severe and among the most common. Active lesions are the target; chronic ones are not retrievable.

Inducing proliferative lupus nephritis

• Proliferative disease (class III or IV, with or without coexisting V) is induced with corticosteroids plus either mycophenolate or cyclophosphamide. Mycophenolate is often preferred — particularly where fertility is a concern and in certain populations — with the low-dose (Euro-Lupus) cyclophosphamide regimen a well-validated alternative. The aim is to switch off the active inflammation before it scars the kidney.

Newer agents and maintenance

• The modern shift is to add a second agent to standard induction for better renal response: belimumab (an anti-BLyS antibody) or voclosporin (a calcineurin inhibitor) have both improved renal outcomes when added to mycophenolate-based therapy in trials. After induction, maintenance — mycophenolate (preferred) or azathioprine — continues for years with the steroids tapered, and hydroxychloroquine is given to all lupus patients because it reduces flares and improves outcomes.

Membranous (class V) lupus

• Class V is membranous lupus nephritis — subepithelial deposits presenting with nephrotic syndrome — and it is managed like membranous nephropathy (the dedicated chapter), with immunosuppression for nephrotic-range or progressive disease. Importantly, class V can coexist with proliferative disease (mixed III/IV + V), in which case the proliferative component drives the aggressive treatment.

Monitoring activity

• Lupus nephritis is monitored serologically and clinically: anti-dsDNA and complement (C3/C4) track renal activity — a rising anti-dsDNA with falling complement signals a flare — alongside proteinuria and kidney function. A repeat biopsy is used when the clinical course changes or relapse is suspected, to re-class the disease and re-guide treatment.

Prognosis and the evidence

• Prognosis is class-dependent: proliferative lupus nephritis, untreated or refractory, carries a significant risk of kidney failure, while treatment markedly improves outcomes, with class and the chronicity score the key predictors. The evidence is rich and moving — mycophenolate and cyclophosphamide are comparably effective for induction (mycophenolate often preferred); belimumab and voclosporin add benefit (BLISS-LN, AURORA); and the field is moving toward combination, lower-steroid regimens. Lupus nephritis can recur after transplantation, though less floridly than some glomerular diseases.

Five fully-built tables.

Table A — The disease at a glance

Table B — The ISN/RPS classes

Table C — Serology and monitoring

Table D — Treatment

Table E — Class V versus proliferative

Visualise & Map

Causal chains, each ending in a named action.

Chain 1 — The immune complex

Anti-dsDNA and immune complexes deposit → classical-pathway complement consumption (low C3 and C4) → glomerular inflammation → lupus nephritis → ACTION: immunosuppress by class.

Chain 2 — The full-house signature

Polyclonal immune-complex deposition → staining for all immunoglobulins and complement → full-house immunofluorescence → ACTION: biopsy to confirm and class.

Chain 3 — The proliferative threat

Endocapillary proliferation and active inflammation → class III/IV → a real risk of kidney failure → ACTION: treat aggressively with induction.

Chain 4 — The membranous variant

Subepithelial deposits → class V membranous lupus → nephrotic syndrome → ACTION: manage like membranous (immunosuppress if nephrotic/progressive).

Chain 5 — The activity markers

Active disease consumes complement and raises anti-dsDNA → the serology tracks activity → a rising anti-dsDNA with falling complement signals a flare → ACTION: monitor anti-dsDNA and complement.

Numbered rules. These numbers are the cross-reference handle for the cases and flowcharts.

Clinical Reasoning

Five cases. Each stops you at a decision before it answers it.

Every mechanism from Level 3 earns a bedside consequence and an action.

Exhaustive. Every rule in the chapter is here.

Safety & Evidence

Panel A — Red flags

Panel B — NEVER DO

Anti-patterns clinicians fall into. Each becomes a Level 22 distractor.

The grade reflects strength of evidence, not importance.

Patient Decisions

Outcomes as natural frequencies. Figures are representative; the direction of effect is given where precise numbers are uncertain.

Apply & Test

Copy-paste chart notes that map to the real decisions in this chapter.

Template 1 — Lupus nephritis class / diagnosis note

• SLE features; renal presentation (proteinuria/hematuria/function): ___.
• Serology: ANA; anti-dsDNA; C3/C4 (both low?) ___.
• Biopsy: full-house IF; ISN/RPS class (I–VI); mixed? ___.
• Activity vs chronicity grading: ___.
• Hydroxychloroquine started/confirmed: ___.

Template 2 — Induction / maintenance / monitoring note

• Induction (proliferative): corticosteroids + mycophenolate / cyclophosphamide ___.
• Newer agent added (belimumab / voclosporin): ___.
• Class V: managed like membranous (IS if nephrotic/progressive) ___.
• Maintenance: mycophenolate / azathioprine; steroid taper; duration ___.
• Monitoring: anti-dsDNA, complement, proteinuria; flare/repeat biopsy ___.

Pre-rounds compression. Rules only.

Active recall. At least one card per objective.

Micro-teaching for rounds. Two scenarios, five steps each.

Metacognition anchored to this chapter's tensions. No answers provided.

1. 1. Mycophenolate and cyclophosphamide are comparable for induction; how do you choose between them for a young patient who may want children?
2. 2. Adding a second agent improves renal response but adds cost and toxicity; how do you decide whom to escalate to combination therapy up front?
3. 3. The field is moving toward lower-steroid regimens; how do you balance sparing steroid toxicity against the speed of controlling active nephritis?
4. 4. Serology tracks activity imperfectly; when does a rising anti-dsDNA with falling complement justify re-biopsy rather than empirical re-treatment?
5. 5. Chronic lesions on the biopsy are not retrievable; how do you weigh the activity-versus-chronicity balance when deciding how hard to immunosuppress?

Nine items, each anchored in this chapter. At least one per objective.