What's the Best Next Step?

Clinical Focus:

• The diagnosis is Systemic Lupus Erythematosus (SLE) with Class IV Lupus Nephritis.

Aetiology/Cause:

• Systemic autoimmune disease characterized by loss of self-tolerance, nuclear autoantigen exposure, and autoantibody production.
• Deposition of circulating antinuclear immune complexes (specifically anti-dsDNA) within the renal glomerular basement membrane and mesangium.
• Activation of the classical complement cascade triggering intense inflammatory cell recruitment, microvascular endothelial damage, and glomerular proliferation.

Clinical Features:

• Constitutional and systemic features including persistent fatigue, low-grade fever, weight loss, and symmetrical inflammatory polyarthralgia.
• Dermatological manifestations such as a photosensitive malar (butterfly) rash, discoid lesions, and oral/nasal ulcers.
• Renal involvement manifesting as peripheral edema, hypertension, hematuria with dysmorphic red blood cells or RBC casts, and proteinuria.
• Multisystem engagement including serositis (pleuritis, pericarditis), hematologic cytopenias, and neuropsychiatric symptoms.

Diagnosis and Investigations: