An ulcer on the foot: a quiz.

A 51-year-old man was admitted with an ulcer on the plantar surface of the left foot. The ulcer had appeared 3 weeks earlier, during a trip to the Solomon Islands, in the south-west Pacific Ocean, after he was stung by a shellfish while snorkelling near a reef. Twenty minutes after being stung, the patient experienced pruritus and a burning sensation at the site of sting. Five hours later, an area of painful erythematous oedema appeared and 5 days later the ulcer developed. Before admission the patient was treated unsuccessfully at other centres with topical antiseptics, econazole, betamethasone 17-benzoate and oral nimesulide, as painrelieving drug. Dermatological examination revealed a linear ulcer, 4 cm in length, surrounded by a 6 × 4 cm purpuric area (Fig. 1). General physical and neurological examination was normal. Laboratory examinations showed leukocytosis (10,100 cells/mm3) and increase in erythrocyte sedimentation rate (first hour: 41 mm). Bacteriological examination was positive for Staphylococcus aureus. What is your diagnosis? See next page for answer. An Ulcer on the Foot: A Quiz