'Oil-drop' pigmentation in psoriatic arthritis.

A 48-year-old man was suffering from psoriasis with psoriatic arthritis for 8 years. His symptoms worsened over the last 3 months and he presented to our hospital with pain and swelling in the knees and ankles, skin lesions over shins, and elbows and discolouration of toenails. He was being treated with methotrexate 15 mg weekly. Examination revealed effusion in both knees. Psoriatic plaques were present over the anterior aspect of the legs, elbows and behind the pinnae. Brownish discolouration of the medial halves of the nails of the great toes (‘oil-drop’ pigmentation, figure 1) was noted with yellowing of the distal nail of the left side. Investigations showed an errythrocyte sedimentation rate of 67 mm/hour, C reactive protein of 32 mg/L and normal blood counts, as well as liver and kidney function tests. Etanercept 50 mg weekly was subcutaneously added after screening for latent tuberculosis, HIV infection and viral hepatitis. At 3 months’ follow-up, skin lesions and inflammation in the joints had disappeared. However, the oil-drop pigmentation persisted, although reduced.