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Answers on p 252.
A 72 year old woman presented with a fleeting rash, lasting several days at a time, on both thighs and lower trunk, over a four month period (fig 1). The eruption was non-pruritic and non-palpable, and occurred on different parts of the legs at different times. She had a 30 year history of seropositive, erosive rheumatoid arthritis and a five year history of secondary Sjogren's syndrome. The patient also had two sinuses on the sole of her right foot, which had been present for a year, and which were being treated conservatively with cleansing and dressing. There were no other new symptoms on admission. Her medication had not changed in over a year, and consisted of methotrexate 15 mg/week (plus folic acid), prednisolone 15 mg/day, diclofenac, thioridazine, and doxepin.
She had a mild normocytic anaemia (haemoglobin concentration 117 g/l) with a raised ferritin level (531 μg/l), while leucocyte and platelet counts were normal. Renal and liver function blood tests, as well as plasma calcium and phosphate concentrations were all within the normal range. The erythrocyte sedimentation rate (Westergren) was 42 mm in the first hour, and C-reactive protein level was 62 mg/l. Rheumatoid factor titre was 320; tests for antinuclear antibodies, antibodies for extractable nuclear antigen, and cryoglobulins were negative.
What is the name given to this rash, and how is the appearance described?
What underlying diseases does it suggest?