Question
A 72-year-old man with only a history of hypertension on hydrochlorothiazide. He presents today with acute, excruciating knee pain. On examination, his knee is warm, mildly erythematous, swollen, and tender to the touch or passive movement. Microscopic examination of joint fluid is shown in the below figure. What is his most likely metabolic derangement?
| A. |
Acute bacterial joint infection
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| B. |
Acute bacterial joint infection
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| C. |
Hyaline cartilage degeneration
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| D. |
Uric acid overproduction
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Show Answer
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Correct Answer � D
Explanation
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Ans. D
The image illustrates monosodium urate crystals, as seen in a fresh preparation of synovial fluid. This is gout.
Most patients with gout are overproducers of uric acid. Hyaline cartilage degeneration is typical of osteoarthritis, which usually has a bland synovial aspirate.
Antibodies to ANA are typical of lupus, rare in an elderly man, and not associated with crystalline fluid.
Bacterial joint infection would have a purulent synovial fluid.
Increased production of inorganic pyrophosphate is a cause of calcium pyrophosphate deposition disease (CPPD; pseudogout), another crystalline arthropathy. CPPD crystals are rod/rhomboid-shaped, weakly birefringent ( images below):
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