Step 1: Pediatric SLE tends to be more severe than adult disease, with renal involvement very common at presentation.
Step 2: The major causes of death in childhood SLE are renal disease (lupus nephritis), severe disease flares, and infections (often linked to immunosuppressive therapy).
Step 3: Of these, lupus nephritis is the leading cause of mortality in children, driving end-stage renal disease and its consequences.
Conclusion: Lupus nephritis is the single most common cause of death in pediatric SLE.
Ref: Nelson Textbook of Pediatrics.