A 38-year-old woman with a history of recurrent gout attacks is started on allopurinol for urate-lowering therapy. One week into treatment, she develops acute severe arthritis, fever, and malaise. Serum uric acid is now 3.8 mg/dL (down from 8.5 mg/dL). Synovial fluid again shows needle-shaped, negatively birefringent crystals. Which mechanism best explains the paradoxical worsening of gout symptoms despite successful lowering of serum uric acid?