Lupus nephritis

Background

• 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).
• 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)

Causes of Glomerulonephritis

• Poststreptococcal glomerulonephritis
• Hemolytic-uremic syndrome
• Henoch-Schonlein purpura
• IgA nephropathy
• Lupus nephritis
• Alport syndrome
• Goodpasture syndrome
• Paraneoplastic

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)