Lupus Nephritis

Lupus nephritis is kidney involvement caused by systemic lupus erythematosus (SLE). Immune-complex injury can progress while symptoms are subtle, so a patient does not need dramatic edema or flank pain to have clinically important renal disease. Suspect renal involvement when proteinuria reaches at least 0.5 g in 24 hours, the urine protein-creatinine ratio is at least 0.5 g/g, or serum creatinine rises more than 30% above baseline. These findings prompt nephrology assessment and kidney biopsy when appropriate. Biopsy classification using the ISN/RPS system separates Classes I–VI; active proliferative Classes III and IV involve at least 50% of glomeruli, with more than 50% segmental or global involvement in the affected glomeruli. The useful bedside pattern is a combination of urine findings, quantified protein loss, changing creatinine/eGFR, blood pressure, fluid status, and disease-activity markers. A positive ANA or anti-dsDNA result supports SLE but does not by itself establish the renal class or determine treatment intensity. Immunosuppression may preserve filtration, but it also creates infection, cytopenia, metabolic, reproductive, and medication-specific risks that require planned surveillance.