Rheumatology · Systemic Lupus Erythematosus
The facts most likely to be tested
Renal biopsy is the gold standard for diagnosis and is indicated in any patient with Systemic Lupus Erythematosus (SLE) who develops proteinuria >0.5 g/day or active urinary sediment.
Class IV (Diffuse Proliferative) lupus nephritis is the most common and severe form, characterized by subendothelial immune complex deposits and a high risk of progression to end-stage renal disease.
Wire-loop lesions on light microscopy are the classic hallmark of Class IV (Diffuse Proliferative) lupus nephritis.
Full-house immunofluorescence staining, showing positive deposits for IgG, IgA, IgM, C3, and C1q, is pathognomonic for lupus nephritis.
Hydroxychloroquine is the foundational therapy for all patients with SLE to prevent flares and reduce the risk of organ damage, including renal involvement.
Mycophenolate mofetil or cyclophosphamide are the preferred induction agents for proliferative forms of lupus nephritis to achieve rapid disease control.
Anti-dsDNA antibody titers and low serum complement (C3 and C4) levels correlate strongly with disease activity and are used to monitor for renal flares.
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A 28-year-old woman with a history of SLE presents for a follow-up visit. She reports no new symptoms, but a routine urinalysis reveals 2+ proteinuria and dysmorphic red blood cells. Her physical exam is notable for malar rash and joint tenderness. Laboratory studies show an elevated anti-dsDNA titer and decreased C3 and C4 levels. Her serum creatinine is 1.1 mg/dL.
What is the most appropriate next step in the management of this patient?
Renal biopsy
The patient has new-onset proteinuria and active urinary sediment in the setting of SLE, which mandates a renal biopsy to determine the histological class and guide immunosuppressive therapy.
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High yield triage
Etiology / Epidemiology
Occurs in 50% of Systemic Lupus Erythematosus patients, most commonly in young females of African, Hispanic, or Asian descent.
Clinical Manifestations
Presents with proteinuria, nephritic syndrome, or nephrotic syndrome; look for active urinary sediment (RBC casts).
Diagnosis
The renal biopsy is the gold standard to determine the ISN/RPS classification (I-VI) and guide therapy.
Treatment
Induction therapy requires Mycophenolate mofetil or cyclophosphamide; teratogenic; maintenance uses Mycophenolate mofetil.
Prognosis
Progression to End-Stage Renal Disease occurs in 10-20% of patients; monitor protein-to-creatinine ratio closely.
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Epidemiology & Etiology
Lupus nephritis is a major cause of morbidity in Systemic Lupus Erythematosus. It disproportionately affects non-Caucasian populations and younger patients. Genetic predisposition and environmental triggers lead to immune complex deposition in the glomerulus.
Pertinent Anatomy
The disease primarily targets the glomerulus, specifically the basement membrane and mesangium. Damage to the podocytes leads to massive proteinuria, while inflammatory cell infiltration causes hematuria.
Pathophysiology
Circulating immune complexes (anti-dsDNA) deposit in the glomerular subendothelial or subepithelial spaces. This triggers the complement cascade, resulting in local inflammation and tissue injury. Chronic damage leads to glomerulosclerosis and interstitial fibrosis.
Clinical Manifestations
Patients often present with nephritic syndrome (hematuria, RBC casts, hypertension) or nephrotic syndrome (edema, hypoalbuminemia, proteinuria >3.5g/day). Active urinary sediment is a hallmark. Rapidly progressive glomerulonephritis is a medical emergency requiring immediate intervention.
Diagnosis
A renal biopsy is mandatory to classify the disease (Class I-VI) and assess for activity versus chronicity. Key diagnostic markers include low C3/C4 levels and high titers of anti-dsDNA antibodies. Monitor renal function via serum creatinine and protein-to-creatinine ratio.
Treatment
Induction therapy for proliferative classes (III/IV) is Mycophenolate mofetil or cyclophosphamide combined with high-dose corticosteroids. Mycophenolate mofetil is strictly contraindicated in pregnancy due to severe birth defects. Maintenance therapy typically utilizes Mycophenolate mofetil or azathioprine to prevent relapse.
Prognosis
Long-term outcomes depend on the histological class and response to induction. End-Stage Renal Disease is the primary long-term risk. Patients require lifelong monitoring of blood pressure and urinary protein excretion.
Differential Diagnosis
IgA Nephropathy: usually follows URI, not associated with systemic lupus
Post-streptococcal GN: history of recent pharyngitis or impetigo
Membranous Nephropathy: primary disease lacks systemic lupus features
Minimal Change Disease: common in children, normal light microscopy
Diabetic Nephropathy: associated with long-standing hyperglycemia and retinopathy