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Mixed Crystal Deposition Disease: Gout, Pseudogout, Basic Calcium Phosphate Arthropathy

Description:

Compensated polarizing microscopy of synovial fluid from a 68-year-old woman with acute monoarthritis of the knee demonstrates a negatively birefringent needle-shaped crystal (1, monosodium urate), a weakly positively birefringent rhomboid-shaped crystal (2, calcium pyrophosphate dihydrate), and basic calcium phosphate crystals (3, alizarin red calcium stain).