A 55-year-old male presents with excruciating pain, erythema, and marked swelling over the first metatarsophalangeal joint (podagra). Arthrocentesis reveals needle-shaped, negatively birefringent crystals under polarized light microscopy. What is the definitive diagnosis?
Answer and explanation
Correct answer: B. Acute Gouty Arthritis
- Step 1: Polarized microscopy differentiates crystal arthropathies based on crystal morphology and birefringence.
- Step 2: Monosodium urate crystals are needle-shaped and demonstrate strong negative birefringence (yellow when parallel to the compensator axis), pathognomonic for acute gouty arthritis.
Answer
Acute Gouty Arthritis.
Why not the others: Pseudogout crystals (calcium pyrophosphate) are rhomboid-shaped with weak positive birefringence; rheumatoid arthritis is an autoimmune synovitis without urate crystals; septic arthritis reveals purulent synovial fluid with intracellular bacteria.
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