The Oil Drop Sign

Excerpt

A 26-year-old woman presented with subacute atraumatic pain and swelling of her right knee and left foot. The right knee was erythematous and warm with an associated joint effusion; the second and third metatarsophalangeal joints and extensor tendons of the left foot were erythematous, warm, and tender. There were well-demarcated erythematous plaques involving the posterior neck. The nail bed of the right fifth digit had a circular area of yellow discoloration with a well-demarcated rim of brown discoloration, resembling a drop of oil (see Fig. 1). Synovial fluid from the knee contained 15,541 WBC/μL, and no organisms were identified. Serologic workup was negative, including antinuclear antibody, anti-double stranded DNA, and rheumatoid factor. Urine and synovial fluid nucleic acid amplification tests for Neisseria gonorrhoeae were negative.

…