Erosive gout is a hallmark of severe disease and an indication to begin urate-lowering therapy, which can be started concurrently during a gout flare, to prevent further articular damage and flare recurrence.1
A 56-year-old male refugee presented to clinic with several days of left knee pain and swelling. His medical history included hypertension, diabetes, and chronic kidney disease. This was preceded by 10 years of intermittent self-resolving joint swelling and pain in his knees, ankles, and elbows, for which he did not seek medical attention.
Joint examination revealed a large left knee effusion, which was aspirated, yielding monosodium urate crystals. Tophi were absent. A radiograph demonstrated a punched-out erosion at the lateral femoral condyle with sclerotic margins, also known as a rat bite erosion or Martel sign (Figure).2 The patient was diagnosed with gout and underwent intraarticular steroid injection for abortive therapy; because of lack of efficacy, this later transitioned to oral prednisone. He was concomitantly started on allopurinol titrated to serum urate < 360 μmol/L. His renal function precluded flare prophylaxis with colchicine. At 1-month follow-up, his joint swelling had improved markedly without further flares. He was referred to the appropriate subspecialties for his comorbidities.
Radiograph of the left knee demonstrating a punched-out erosion at the lateral femoral condyle with sclerotic margins (white arrow).
Gout typically presents with monoarthritis of the lower extremities but can also manifest with oligoarthritis or polyarthritis in severe, protracted disease.3 The majority of erosions stemming from gout occur in the first metatarsophalangeal joint, with femoral involvement being relatively uncommon.4 Factors associated with erosive gout include older age, longer duration of gout, presence of tophi, and synovial hypertrophy.4
Footnotes
The authors declare no conflicts of interest relevant to this article. Research ethics board approval was not required as this project did not constitute research, as per the Sunnybrook Research Institute Research Ethics Board. The authors have obtained the patient’s written informed consent to publish the material.
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