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Difficulty: MediumRheumatology and Immunology

A 74-year-old man is brought to the emergency department by his daughter due to severe pain and swelling in his right knee that began 18 hours ago. He cannot bear weight on the affected leg. His medical history is significant for primary hyperparathyroidism, osteoarthritis, and stage 3 chronic kidney disease. His temperature is 38.0°C (100.4°F), blood pressure is 142/88 mmHg, and pulse is 96/min. Physical examination reveals a swollen, warm, and erythematous right knee with a palpable effusion. Range of motion is severely limited by pain. Arthrocentesis yields 25 mL of cloudy yellow synovial fluid. Laboratory analysis of the fluid reveals a leukocyte count of 32,000/mm³ with 82% neutrophils. Polarized light microscopy of the fluid demonstrates rhomboid-shaped, weakly positively birefringent crystals. Gram stain of the synovial fluid shows no organisms. Which of the following is the most appropriate next step in the management of this patient?

  1. A
    Initiation of intravenous vancomycin and ceftriaxone
  2. B
    Initiation of oral allopurinol therapy
  3. Intra-articular injection of triamcinoloneAnswer
  4. D
    Measurement of serum uric acid concentration
  5. E
    Arthroscopic joint irrigation and debridement

Answer

Intra-articular injection of a glucocorticoid, such as triamcinolone, is the most appropriate next step.
The correct answer is an intra-articular glucocorticoid injection. The patient presents with acute monoarthritis caused by calcium pyrophosphate deposition (CPPD) disease, as evidenced by the rhomboid-shaped, weakly positively birefringent crystals. First-line therapies for acute CPPD flares include NSAIDs, colchicine, and intra-articular glucocorticoids. Given the patient's stage 3 chronic kidney disease, NSAIDs are contraindicated and colchicine carries an increased risk of toxicity. Therefore, an intra-articular glucocorticoid injection is the safest and most effective targeted therapy.

Step-by-Step Solution

1
Analyze the patient's synovial fluid results in the context of his symptoms.
The fluid shows 32,000 leukocytes/mm³ with 82% neutrophils and rhomboid-shaped, weakly positively birefringent crystals.
This confirms an acute inflammatory crystal arthropathy, specifically calcium pyrophosphate deposition (CPPD) disease, commonly known as pseudogout. The patient's underlying hyperparathyroidism is a known risk factor.
2
Evaluate the patient's medical history for contraindications to standard acute gout/pseudogout therapies.
The patient has stage 3 chronic kidney disease (CKD).
Nonsteroidal anti-inflammatory drugs (NSAIDs) are contraindicated in advanced CKD, and colchicine requires careful dosing due to decreased renal clearance, making them less favorable options.
3
Select the most appropriate and safest acute treatment for a monoarticular flare.
Intra-articular glucocorticoid injection.
It provides rapid, localized anti-inflammatory relief with minimal systemic side effects, making it the ideal choice for a patient with a single affected joint and significant renal impairment.

Key Concept

Diagnosis and acute management of calcium pyrophosphate deposition (CPPD) disease (pseudogout), recognizing treatment constraints in patients with chronic kidney disease.
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Topics

Rheumatology and Immunology

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