Leg ulceration in a young woman

A 21 year old woman presented to her local emergency department with a painful necrotic blister on her left lower leg, which she thought might have followed an insect bite. Doctors diagnosed an abscess, which was treated with oral antibiotics. Three months later she presented with another presumed abscess in her right leg. Intravenous antibiotics were given and multiple surgical debridements were carried out over a two week period. Despite these interventions, the lesion rapidly advanced, and the patient became systemically unwell (fig 1). The admitting orthopaedic team suspected necrotising fasciitis and contemplated amputation of the leg below the knee.

Her C reactive protein concentration was 350 mg/l; white blood cell count 35×10/l; blood film, lymphocyte subsets, and serum protein electrophoresis were normal; and vasculitic and autoimmune screens and hepatitis serology were negative. Blood cultures and tissue microbiology for bacteria, fungi, and mycobacteria were also negative.

The extent of her deterioration required her to be transferred to the intensive care unit, where she was reviewed by dermatologists. They made an immediate diagnosis based on her clinical features and apparent lack of an infective cause.