Pustular ulcer with a blistering border

Case history

Over a three-week period, a 43-year-old woman developed a rapidly expanding necrotic ulcer over her right medial ankle. The ulcer had a pustular and haemorrhagic base and a peripheral dusky blistering edge. Cultures for bacteria and fungi were negative. A skin biopsy from the edge of the lesion showed sheets of neutrophils undergoing leucocytoclasis and filling the dermis. The patient had a known history of Crohn’s disease.