Ultrasonography for diagnosing atypical gout. Two case reports.

Gout is characterized by the deposition of monosodium urate crystals on the surface of the articular cartilage, within periarticular tissues, and within bone and skin. The diagnosis rests on identification of the crystals in joint fluid or a tophus. However, joint aspiration is not always feasible, and the presentation may be atypical. We describe two cases of chronic gouty arthritis misdiagnosed as psoriatic arthritis. Ultrasonography of the bone and joints disclosed two patterns recently described as highly suggestive of gout, namely, the double-contour appearance of the cartilage and the snowstorm appearance of the synovial membrane. In addition, ultrasonography was useful for guided aspiration of joint fluid or other material containing monosodium urate crystals. Thus, ultrasonography may contribute to improve the diagnosis and treatment of gout.