Lupus nephritis

Lupus nephritis (LN) is renal involvement in Systemic lupus erythematosus, caused by deposition of immune complexes in the glomeruli, which activates complement and causes inflammation, scarring, and progressive kidney damage. It is clinically evident in 50-60% of SLE patients and is histologically present in the majority, even those without clinical signs of renal disease. Lupus nephritis is a major determinant of SLE prognosis — untreated proliferative disease (class III/IV) leads to end-stage kidney disease (ESKD) in a substantial proportion of patients. The emergency physician encounters LN as new-onset nephritic or nephrotic syndrome in a patient with SLE features, acute renal failure during a lupus flare, or complications of immunosuppressive therapy (infection, cytopenias).

Background

• SLE predominantly affects women of childbearing age (female-to-male ratio 9:1); lupus nephritis typically presents at ages 20-40 years
• Higher incidence and more severe disease in African Americans, Hispanics, and Asians
• Males with SLE have a higher rate of renal involvement and worse prognosis than females
• Children with SLE have more frequent and more aggressive renal disease than adults
• Lupus nephritis usually arises within the first 5 years of SLE diagnosis; may be the presenting manifestation of SLE
• Delayed diagnostic biopsy >6 months is associated with a 9-fold increased risk of ESKD

ISN/RPS Classification (determines treatment and prognosis)

Class	Description	Clinical significance
I	Minimal mesangial	Normal urinalysis; no treatment needed; excellent prognosis
II	Mesangial proliferative	Microscopic hematuria ± mild proteinuria; usually mild; glucocorticoids if needed
III	Focal proliferative (<50% of glomeruli)	Active nephritis; hematuria, proteinuria, rising creatinine; requires immunosuppression
IV	Diffuse proliferative (≥50% of glomeruli)	Most common and most severe; nephritic ± nephrotic features; highest risk of ESKD; aggressive immunosuppression required
V	Membranous	Nephrotic syndrome predominates; proteinuria may be massive; may overlap with III/IV
VI	Advanced sclerotic (>90% sclerosed)	ESKD; irreversible; renal replacement therapy; immunosuppression not helpful

• Class IV is the most common biopsy finding and carries the worst untreated prognosis
• Mixed classes (III/V or IV/V) have features of both proliferative and membranous disease
• Class can transform — mild disease may progress to severe proliferative disease; repeat biopsy may be needed for flares

Mechanism

• Anti-dsDNA and other autoantibodies form immune complexes → deposit in mesangium and glomerular capillary walls
• Complement activation (classical pathway) → C3, C4 consumption → low serum C3 and C4
• Inflammation → cellular proliferation, crescent formation, fibrinoid necrosis
• Chronic inflammation → sclerosis and irreversible nephron loss

Clinical features

Presentations the EM physician will encounter

New-onset renal disease in a known SLE patient

• Hematuria (gross or microscopic), proteinuria (detected on urinalysis)
• Edema (periorbital, lower extremity, or generalized if nephrotic)
• Hypertension (new or worsening)
• Rising creatinine, decreased urine output
• Often concurrent with other signs of lupus flare: fever, malar rash, arthritis, oral ulcers, pleurisy, pericarditis, cytopenias

SLE presenting with renal disease as the first manifestation

• Young woman with unexplained nephritic or nephrotic syndrome
• May have undiagnosed SLE — look for constitutional symptoms, rash, arthritis, photosensitivity, oral ulcers, alopecia, serositis
• Any young woman with GN should be tested for SLE

Lupus nephritis flare

• Known LN patient with worsening proteinuria, rising creatinine, new hematuria, or declining complement levels
• May be triggered by medication noncompliance, infection, pregnancy, UV exposure
• Rising anti-dsDNA + falling C3/C4 often precedes clinical flare by weeks

Rapidly progressive glomerulonephritis (RPGN)

• Class IV with crescents — renal function deteriorates over days to weeks
• Nephritic sediment + rapidly rising creatinine
• Nephrology emergency — urgent biopsy and aggressive immunosuppression needed

Complications of immunosuppressive treatment

• Infection: the most common cause of death in actively treated LN patients; opportunistic infections from cyclophosphamide, mycophenolate, rituximab, steroids
• Cytopenias: from cyclophosphamide, mycophenolate, azathioprine; may present with neutropenic fever
• Steroid side effects: hyperglycemia, psychosis, adrenal crisis on abrupt withdrawal, AVN of femoral head
• Thrombotic microangiopathy (TMA): may occur in LN, especially with antiphospholipid antibodies — presents with microangiopathic hemolytic anemia, thrombocytopenia, renal failure; consider concurrent antiphospholipid syndrome

Key clinical signs suggesting SLE in an undiagnosed patient

• Malar (butterfly) rash — erythematous rash over cheeks/nasal bridge sparing nasolabial folds
• Photosensitivity
• Oral/nasal ulcers (often painless)
• Arthritis/arthralgias (symmetric, non-erosive)
• Serositis (pleuritis, pericarditis)
• Alopecia
• Raynaud phenomenon
• Cytopenias: leukopenia, lymphopenia, thrombocytopenia, hemolytic anemia (Coombs-positive)

Differential diagnosis

Nephritic/nephrotic syndrome in a young patient

• Lupus nephritis (this page)
• IgA nephropathy — most common GN worldwide; synpharyngitic hematuria; normal complement
• Post-streptococcal GN — post-infectious latent period; low C3 (normalizes in 6-8 weeks)
• ANCA-associated vasculitis (GPA, MPA) — ANCA positive; normal complement
• Anti-GBM disease — anti-GBM antibodies; normal complement; may have pulmonary hemorrhage
• MPGN / C3 glomerulopathy — persistently low C3
• Focal segmental glomerulosclerosis — nephrotic; biopsy diagnosis; normal complement
• Minimal change disease — nephrotic; steroid-responsive; normal complement
• Membranous nephropathy — nephrotic; may be secondary to SLE, malignancy, hepatitis B
• Thrombotic thrombocytopenic purpura (TTP) — MAHA, thrombocytopenia, AKI, fever, neurologic changes; can coexist with SLE
• Antiphospholipid syndrome nephropathy — may occur with or without SLE; TMA pattern

Lupus nephritis complement pattern

• Low C3 AND low C4 is characteristic of active lupus nephritis (classical pathway activation)
• Distinguishes from PSGN (low C3, usually normal or slightly low C4) and ANCA/anti-GBM disease (normal complement)

Evaluation

ED workup

• Urinalysis with microscopy: hematuria (dysmorphic RBCs, RBC casts), proteinuria, sterile pyuria
• Spot urine protein:creatinine ratio: quantifies proteinuria; nephrotic range (>3.5) suggests class V or severe III/IV
• BMP/CMP: creatinine (baseline and trending), BUN, potassium (hyperkalemia risk), bicarbonate
• CBC: cytopenias (leukopenia, lymphopenia, thrombocytopenia, Coombs-positive hemolytic anemia — all support SLE diagnosis)
• Albumin: low if nephrotic
• Blood pressure: hypertension common in active disease

SLE serologic workup (initiate from ED)

Test	Significance
ANA	Sensitive screening test for SLE (>95% positive); not specific; negative ANA makes SLE very unlikely
Anti-dsDNA	Highly specific for SLE; correlates with disease activity and renal involvement; rising titers predict flare
C3, C4 complement	Low C3 AND low C4 = active lupus nephritis (classical pathway consumption); serial monitoring useful for tracking flare activity
Anti-Smith (anti-Sm)	Highly specific for SLE (but less sensitive than anti-dsDNA)
Antiphospholipid antibodies (anticardiolipin, lupus anticoagulant, anti-β2-glycoprotein I)	Identify concurrent antiphospholipid syndrome → increased thrombosis risk, TMA
ESR, CRP	Often elevated; ESR tends to track disease activity in SLE (CRP may be normal unless infection or serositis is present)

• Trend creatinine: compare to baseline; a rising creatinine with active sediment suggests active nephritis
• Renal ultrasound: normal or enlarged kidneys in acute disease; small kidneys suggest chronic damage

Renal biopsy

• Gold standard for diagnosis and classification — determines ISN/RPS class, activity/chronicity indices, and guides treatment
• Not performed in the ED — arranged by nephrology
• Indications: new-onset proteinuria (>500 mg/day), active urinary sediment, rising creatinine, suspected flare in known LN patient
• Biopsy results fundamentally change management — mild mesangial disease (class I/II) needs minimal treatment; diffuse proliferative disease (class IV) requires aggressive immunosuppression

Management

ED management of acute lupus nephritis/flare

• Manage life-threatening complications first:
  • Hypertensive emergency: IV antihypertensives (nicardipine, labetalol); loop diuretics for volume overload (see Hypertensive emergency)
  • Hyperkalemia: standard protocols (see Hyperkalemia)
  • Pulmonary edema: furosemide, oxygen, positive pressure ventilation
  • Severe AKI: urgent dialysis if refractory hyperkalemia, acidosis, volume overload, or uremic symptoms
• Fluid and sodium restriction if edematous or volume-overloaded
• Loop diuretics (furosemide) for edema and volume-mediated hypertension
• Do NOT start immunosuppressive therapy in the ED — this requires biopsy-guided decision-making by nephrology/rheumatology
• Exception: if RPGN is strongly suspected (rapidly rising creatinine + active sediment), pulse IV methylprednisolone (500-1000 mg) may be initiated after nephrology telephone consultation while biopsy is arranged — time is critical for kidney survival

Medication safety in the ED

• Continue hydroxychloroquine — it should not be discontinued; it reduces flare risk and has renal-protective effects
• Continue existing immunosuppressants unless the patient is septic (in which case, hold immunosuppression and consult rheumatology/nephrology)
• Avoid NSAIDs — nephrotoxic; may worsen renal function and hypertension
• Avoid nephrotoxic agents: aminoglycosides, IV contrast (if possible; discuss risk-benefit if imaging is critical)
• ACE inhibitors/ARBs: standard chronic therapy for proteinuria reduction; may need to be held in acute AKI with hyperkalemia

Disease-specific treatment (nephrology/rheumatology-directed)

• All classes: hydroxychloroquine (background therapy) + ACE inhibitor/ARB (for proteinuria >500 mg/day)
• Class I/II: monitoring; glucocorticoids for flare; no immunosuppression usually needed
• Class III/IV (and mixed III/V, IV/V):
  • Induction: glucocorticoids + mycophenolate mofetil (first-line) OR IV cyclophosphamide (for severe/refractory disease)
  • Pulse IV methylprednisolone (500-1000 mg daily for 3 days) followed by oral prednisone taper
  • Maintenance: mycophenolate mofetil (superior to azathioprine) for at least 3 years
• Class V (membranous): glucocorticoids + mycophenolate mofetil; ACE inhibitor/ARB
• Class VI: renal replacement therapy (dialysis or transplant); immunosuppression not indicated
• Newer agents: belimumab (anti-BAFF; FDA-approved for LN as add-on therapy), voclosporin (calcineurin inhibitor; FDA-approved for LN), rituximab (B-cell depletion; used for refractory disease)

Disposition

• Admit:
  • New-onset lupus nephritis with significant proteinuria, active sediment, or elevated creatinine
  • Lupus nephritis flare with worsening renal function
  • RPGN or rapidly rising creatinine — urgent nephrology consultation
  • Severe hypertension, hyperkalemia, pulmonary edema
  • Concurrent severe lupus flare involving other organs (cerebritis, pulmonary hemorrhage, severe cytopenias, serositis)
  • Infection in an immunosuppressed LN patient
• Discharge with close follow-up:
  • Known stable LN patient with mild abnormality on labs and no significant change from baseline
  • Ensure nephrology AND rheumatology follow-up within 48-72 hours
  • Emphasize medication compliance (especially hydroxychloroquine and immunosuppressants)
• Counseling points:
  • Never stop hydroxychloroquine without specialist guidance — discontinuation increases flare risk
  • Sun protection (UV exposure triggers SLE flares)
  • Report signs of flare: edema, decreased urine output, foamy/bloody urine, joint pain, rash, fever
  • Report signs of infection immediately (immunosuppressed patients)
  • Pregnancy planning: lupus nephritis has major implications for pregnancy; active disease should be in remission before conception; requires close coordination with maternal-fetal medicine, nephrology, and rheumatology

See Also

• Nephritic syndrome
• Nephrotic syndrome
• Focal segmental glomerulosclerosis
• Acute kidney injury
• Hypertensive emergency
• Hyperkalemia
• Systemic lupus erythematosus
• Antiphospholipid syndrome
• Goodpasture syndrome
• Thrombotic thrombocytopenic purpura

External Links

• StatPearls — Lupus Nephritis
• Medscape — Lupus Nephritis
• Int J Womens Health — Understanding lupus nephritis: diagnosis, management, and treatment options (2012)
• Rheumatology — Ten tips in lupus nephritis management (2025)
• Kidney Int — Revision of the ISN/RPS classification for lupus nephritis (2018)