History: 6896vf Sudden onset of a blistering lesion on the leg. She has Chronic lymphatic leukaemia last treated by chemotherapy a few months ago. Differential of Sweet's syndrome or Herpes simplex but after discussion consider bullous insect bite reaction with underlying CLL. Biopsy of edge of blister.

Description: Epidermal necrosis

Comments: Sections show a biopsy of skin in which there is extensive necrosis of the epidermis. Only the basal epidermis remains viable. There is a moderately dense superficial, mid and deep dermal infiltrate of lymphocytes and numerous eosinophils. The lymphocytes are predominantly perivascular in location whilst the oesinophils are predominantly interstitial in location. Very sparse neutrophils are also noted. A necrotizing arthropod bite reaction would be favoured. Exaggerated bite reaction can be associated with CLL and other leukaemias.