Immune-complex glomerulonephritis in SLE; ISN/RPS class determines therapy.
Also known as: lupus nephritis, SLE nephritis, LN, class IV lupus nephritis, diffuse proliferative lupus nephritis
Overview
Glomerulonephritis occurring in patients with systemic lupus erythematosus, mediated by immune complex deposition (anti-dsDNA, anti-nucleosome) and complement activation. Classified into six ISN/RPS classes that guide therapy: I (minimal mesangial), II (mesangial proliferative), III (focal proliferative), IV (diffuse proliferative), V (membranous), and VI (advanced sclerosing).
Epidemiology
Develops in up to 50% of patients with SLE within 5 years of diagnosis. Higher prevalence and severity in Black, Hispanic, and Asian patients. Female predominance reflects underlying SLE epidemiology (~9:1). Lupus nephritis is one of the strongest predictors of SLE-related morbidity and mortality.
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Question 1RenalMedium
A 35-year-old woman has hematuria, red blood cell casts, and 3+ proteinuria. Serum creatinine is 2.8 mg/dL, C3 and C4 are low, antinuclear antibody is 1:1280, and anti-double-stranded DNA antibody is positive. Renal biopsy shows diffuse proliferative glomerulonephritis with 'full-house' immunofluorescence (IgG, IgM, IgA, C3, C1q). Which of the following is the most likely diagnosis?
ALupus nephritis class IV
BMembranoproliferative glomerulonephritis type I
CIgA nephropathy
DPost-streptococcal glomerulonephritis
Reveal answer & full explanation
Correct answer: A — Lupus nephritis class IV
ALupus nephritis class IV✓
BMembranoproliferative glomerulonephritis type I
CIgA nephropathy
DPost-streptococcal glomerulonephritis
Why Lupus nephritis class IV is correct
Full-house immunofluorescence (IgG, IgM, IgA, C3, C1q) is characteristic of lupus nephritis.
Positive anti-double-stranded DNA with low C3 and C4 indicates active systemic lupus erythematosus with immune-complex consumption.
Diffuse proliferative (class IV) is the most common and most severe class; the active sediment (RBC casts, heavy proteinuria) and elevated creatinine fit it.
Why the others are wrong
Membranoproliferative glomerulonephritis type I - also lowers complement (buzzword trap), but lacks full-house immunofluorescence and is not associated with anti-double-stranded DNA or lupus serologies.
IgA nephropathy - shows isolated mesangial IgA deposits with normal complement and negative lupus serologies, unlike the full-house pattern here.
Post-streptococcal glomerulonephritis - depresses C3 (not typically C4), follows a streptococcal infection, and lacks anti-double-stranded DNA and full-house staining (anchoring on low complement).
Question 2RenalMedium
A 45-year-old female with class IV (proliferative) lupus nephritis has been in complete renal remission (proteinuria <0.5 g/day, stable eGFR) on mycophenolate mofetil (MMF) plus hydroxychloroquine for 3 years. She asks how long she must remain on maintenance immunosuppression. Which of the following is the most appropriate approach?
ATaper off all immunosuppression after 1 year of sustained remission
BDiscontinue mycophenolate after 6 months, continue hydroxychloroquine
CContinue immunosuppression with individualized reassessment for a cautious taper; hydroxychloroquine indefinitely
DSwitch to low-dose prednisone monotherapy for long-term maintenance
Reveal answer & full explanation
Correct answer: C — Continue immunosuppression with individualized reassessment for a cautious taper; hydroxychloroquine indefinitely
ATaper off all immunosuppression after 1 year of sustained remission
BDiscontinue mycophenolate after 6 months, continue hydroxychloroquine
CContinue immunosuppression with individualized reassessment for a cautious taper; hydroxychloroquine indefinitely✓
DSwitch to low-dose prednisone monotherapy for long-term maintenance
Why Continue immunosuppression with individualized reassessment for a cautious taper; hydroxychloroquine indefinitely is correct
After induction, lupus nephritis maintenance with MMF (typically 1–2 g/day) or azathioprine is generally continued for several years before any withdrawal is considered.
KDIGO and EULAR/ERA support a cautious, individualized taper once complete renal remission has been sustained (often around 3 years), rather than a fixed additional course for everyone.
This patient already has 3 years of complete remission, so the decision now is whether to begin a gradual, closely monitored taper — not to reset the clock with another fixed multi-year course.
Renal flare risk after withdrawal is meaningful, so tapering should be slow and paired with ongoing surveillance of proteinuria, serologies, and eGFR.
Hydroxychloroquine is continued indefinitely in all SLE patients: it reduces flares, damage accrual, cardiovascular events, and thrombosis.
Why the others are wrong
Taper off all immunosuppression after 1 year of sustained remission — Right concept (eventual taper) but wrong timing; one year of remission is too brief and premature withdrawal carries a substantial flare risk.
Discontinue mycophenolate after 6 months, continue hydroxychloroquine — Anchoring on stopping too early; six months is far too short for maintenance in class IV disease, well before a taper should be considered.
Switch to low-dose prednisone monotherapy for long-term maintenance — Confused-with adequate maintenance; steroid monotherapy lacks disease-modifying benefit and adds cumulative steroid toxicity, so it does not replace MMF or azathioprine.
Hydroxychloroquine monitoring: annual ophthalmologic screening for retinal toxicity after 5 years of use.
ACE inhibitors should be continued indefinitely for BP control and antiproteinuric effect.
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Loss of immune tolerance to nuclear antigens generates autoantibodies (anti-dsDNA, anti-Sm, anti-nucleosome). Immune complexes deposit in mesangium (classes I-II), subendothelial space (classes III-IV — leading to severe inflammation and crescents), and subepithelial space (class V — analogous to primary membranous nephropathy). Complement activation drives endothelial and tubulointerstitial injury. The 'full-house' immunofluorescence pattern (IgG, IgA, IgM, C3, C1q) is characteristic.
Clinical presentation
Symptoms
Hematuria, proteinuria, peripheral edema
Hypertension (often severe in class IV)
Constitutional and extrarenal SLE features — fatigue, arthralgia, malar rash, photosensitivity, oral ulcers, alopecia, Raynaud, serositis
Acute kidney injury or rapidly progressive course in severe class III/IV
Kidney biopsy is essential for any SLE patient with proteinuria >0.5 g/day, active urine sediment, or unexplained creatinine rise. Biopsy provides ISN/RPS class, activity index (acute injury — reversible), and chronicity index (irreversible damage). The 2024 ACR/EULAR guidelines emphasize biopsy-driven therapy.
Direct Coombs, haptoglobin, LDH, reticulocyte count if hemolysis suspected
Hepatitis B and C, HIV, TB screening (prior to immunosuppression)
Pregnancy test in reproductive-age women
Imaging
Renal ultrasound — normal-sized kidneys early; atrophy with chronic disease
Echocardiogram if pericardial effusion or pulmonary hypertension suspected
Diagnostic algorithm
ISN/RPS class
Histology
Typical presentation
Therapy approach
I
Minimal mesangial
Normal urine or trace proteinuria
Supportive only
II
Mesangial proliferative
Mild proteinuria, hematuria
Supportive; treat extrarenal lupus
III
Focal proliferative (<50% glomeruli)
Active sediment, proteinuria
Induction + maintenance immunosuppression
IV
Diffuse proliferative (≥50% glomeruli)
Nephritic syndrome, AKI, hypertension
Aggressive induction (steroids + MMF or CYC + belimumab/voclosporin)
V
Membranous
Nephrotic syndrome, often normal GFR
Steroids + MMF / CNI / CYC if nephrotic
VI
Advanced sclerosing (>90% sclerosed)
ESKD
Supportive; prepare for RRT
ISN/RPS classification of lupus nephritis — biopsy class drives therapy.
Treatment
First-line
Hydroxychloroquine for all SLE patients (300-400 mg/day; check ophtho for retinal toxicity annually after 5 years)
RAAS blockade — ACE inhibitor (lisinopril, enalapril) or ARB (losartan, valsartan) for proteinuria
Blood pressure control (<125/75 if proteinuric)
Pneumococcal, influenza, COVID, and HPV vaccination before immunosuppression
Class I or II — supportive care; treat extrarenal lupus only
Class III / IV (proliferative) — induction
Glucocorticoids — IV methylprednisolone pulse (250-1000 mg × 3 days) then prednisone 0.5-1 mg/kg/day tapered over 6 months
Combine with one of: mycophenolate mofetil (target 2-3 g/day), low-dose IV cyclophosphamide (Euro-Lupus regimen — 500 mg q2 weeks × 6 doses), or high-dose IV cyclophosphamide (NIH regimen)
Add belimumab (anti-BLyS monoclonal) or voclosporin (calcineurin inhibitor) as 'triple therapy' per 2024 ACR — improves response rates
Class III / IV — maintenance (after induction response)
Mycophenolate mofetil 1-2 g/day or azathioprine 1.5-2 mg/kg/day
Continue belimumab or voclosporin if used in induction
Taper steroids to lowest effective dose (target <7.5 mg/day by 6 months)
Duration ≥3 years from complete response
Class V (membranous)
If nephrotic-range proteinuria or worsening renal function: corticosteroids + mycophenolate mofetil, calcineurin inhibitor (tacrolimus, cyclosporine), or cyclophosphamide
If sub-nephrotic and stable: RAAS blockade + hydroxychloroquine
Mixed III+V or IV+V
Treat as proliferative disease with induction + maintenance regimens
Class VI (advanced sclerosing)
Supportive nephroprotective care; prepare for renal replacement therapy
Immunosuppression only for extrarenal disease
Second-line / adjunct
Rituximab — refractory disease or contraindication to cyclophosphamide/MMF
Obinutuzumab in clinical trials
Plasmapheresis for severe AKI with crescents or coexisting antiphospholipid syndrome / TMA
Renal transplantation for ESKD — outcomes generally good; consider delaying until SLE is quiescent
Complications
Progression to ESKD (10-30% within 10 years for class IV without treatment)
Cardiovascular disease and accelerated atherosclerosis
Infection from immunosuppression
Avascular necrosis, osteoporosis from chronic corticosteroids
Pregnancy complications — preeclampsia, fetal loss; flares more common in active disease
Antiphospholipid syndrome with renal microangiopathy
PANCE pearls
Always biopsy SLE patients with new proteinuria >0.5 g/day, active urine sediment, or unexplained AKI — the class determines therapy.
Hydroxychloroquine reduces flares and improves renal outcomes in all classes; do not omit.
2024 ACR guideline endorses 'triple therapy' (steroids + MMF or cyclophosphamide + belimumab or voclosporin) for proliferative LN.
Activity index predicts response to therapy; chronicity index predicts long-term outcome.
Rising anti-dsDNA and falling C3/C4 may herald a flare even before clinical changes.
References
ACR 2024 — Sammaritano LR et al. 2024 American College of Rheumatology Guideline for the Treatment of Lupus Nephritis (Arthritis Rheumatol 2024)
KDIGO 2024 — KDIGO 2024 Clinical Practice Guideline for the Management of Lupus Nephritis (Kidney Int 2024)
ISN/RPS 2018 — Bajema IM et al. Revision of the International Society of Nephrology/Renal Pathology Society classification of lupus nephritis (Kidney Int 2018;93:789-796)
BLISS-LN — Furie R et al. Two-year, randomized, controlled trial of belimumab in lupus nephritis (NEJM 2020;383:1117-1128)
AURORA-1 — Rovin BH et al. Efficacy and safety of voclosporin versus placebo for lupus nephritis (Lancet 2021;397:2070-2080)
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