Abstract

Synovial fluid (SF) aspiration cytology is a useful diagnostic tool. For patients with gouty arthritis, the diagnosis is confirmed by the presence of monosodium uric acid (MSU) crystals in the SF, and these crystals are long, pointed ended and needle-shaped and they show strongly negative birefringence. Sometimes, it is difficult to diagnosis between gouty arthritis and other type of inflammatory arthritis. We experienced two unusual cases of gouty arthritis that we performed SF analysis for. The first patient was a 35 year old male who presented with relatively typical clinical symptoms with hyperuricemia, but the SF showed acute inflammatory cells without crystals on light microscopy. Only a few suspected crystals of MSU were identified on polarizing microscopy. The second patient was a 45 year old male who presented with atypical symptoms and pain and swelling of the left ankle and knee joint for 3 weeks. The uric acid level in the serum and urine was increased, but not over the normal limit. However, on light and polarizing microscopy, there were numerous MSU crystals in the SF. Conclusively, in some cases of gouty arthritis, the crystals are not identified on light microscopy or the uric acid level is not dramatically increased. So, the polarizing microscopy, the clinical information and the laboratory findings are all included in the work-up when evaluating the SF cytology of arthritis patients.

• Keywords: Gout;Synovial fluid;Monosodium urate;Cytology