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Lupus nephritis (LN) is one of the most serious complications of systemic lupus erythematosus (SLE). It occurs in 30–70% of patients and is a major determinant of prognosis. Regular urine testing and BP monitoring are essential for early detection of treatable disease.
ℹ️ About
- Seen in 30–70% of those with SLE, especially in younger women and Afro-Caribbean patients.
- Strongly influences morbidity, mortality, and progression to chronic kidney disease (CKD).
- Immune-mediated inflammation of the glomeruli due to immune complex deposition (dsDNA + complement).
Presentation 🩺
- Microscopic or macroscopic haematuria.
- Proteinuria (may progress to nephrotic syndrome with oedema, ascites, hyperlipidaemia).
- Rising serum creatinine, reduced GFR.
- Hypertension (common, may be severe).
- Renal artery or vein thrombosis (esp. in antiphospholipid antibody-positive patients).
- Can be asymptomatic – detected on screening urinalysis.
Aetiology & Pathophysiology 🧬
- Immune complex deposition: dsDNA-anti-dsDNA immune complexes deposit in glomeruli → activate complement → inflammation & damage.
- Complement dysregulation: Low C3/C4 and low C1q during active nephritis.
- Genetic susceptibility: HLA-DR2, DR3, and polymorphisms in complement pathway genes.
- Environmental triggers: Infections, UV exposure, and smoking can precipitate flares.
ISN/RPS Classification of Lupus Nephritis (2003, updated 2018) 📊
- Class I: Minimal mesangial LN (immune deposits, normal light microscopy).
- Class II: Mesangial proliferative LN (mesangial hypercellularity & matrix expansion).
- Class III: Focal LN (<50% glomeruli; segmental or global proliferative lesions).
- Class IV: Diffuse LN (>50% glomeruli; segmental/global proliferative). Most severe form.
- Class V: Membranous LN (subepithelial deposits; nephrotic syndrome).
- Class VI: Advanced sclerosing LN (≥90% glomeruli sclerosed → ESRD).
Signs of Histological Activity 🔬
- Endocapillary hypercellularity with leukocyte infiltration.
- Karyorrhexis (nuclear fragmentation).
- Cellular or fibrocellular crescents.
- Subendothelial deposits on EM (“wire-loop” lesions).
- Intraluminal immune aggregates.
- Fibrinoid necrosis, GBM rupture.
Investigations 🔎
- Serology: ANA positive; anti-dsDNA correlates with activity; anti-Ro/La may co-exist.
- Complement: C3, C4, C1q often low in active nephritis.
- CRP: Typically normal even in flares (contrast with infection, where CRP rises).
- Urine: Proteinuria (dipstick/24h), haematuria, cellular casts.
- Bloods: U&E, eGFR, FBC (for cytopenias), lipids.
- Imaging: Renal ultrasound to rule out obstruction.
- Definitive: Renal biopsy - required for classification & guiding therapy.
Management 💊
- Class I/II: Usually conservative ± hydroxychloroquine. BP & urine monitoring.
- Class III/IV (proliferative):
- Induction: High-dose glucocorticoids + mycophenolate mofetil (MMF) or IV cyclophosphamide.
- Maintenance: MMF or azathioprine + low-dose steroids.
- Class V: If nephrotic-range proteinuria → MMF or cyclophosphamide ± steroids.
- Class VI: Supportive care (ACE inhibitors/ARBs for proteinuria, BP control, dialysis or transplant for ESRD).
- Biologics: Rituximab or belimumab in refractory disease.
- General measures: Hydroxychloroquine for all unless contraindicated; BP control (ACEi/ARB); avoid nephrotoxins (NSAIDs); vaccinations; sun protection.
Clinical Pearls ✨
- 🧪 dsDNA rises + complement falls = active flare.
- ⚡ CRP normal in active LN but rises with infection → helps distinguish flare vs sepsis.
- 👩⚕️ Always screen for antiphospholipid antibodies in SLE with renal disease (risk of thrombosis).
- ❤️ ACE inhibitors/ARBs are renoprotective in proteinuria (↓ intraglomerular pressure).
- 🧬 Monitoring: BP, urinalysis, U&E, dsDNA, complements every 1–3 months in active disease.
