An 87 year old woman presented with a non-itchy rash that began three weeks ago on the abdomen. Since then it had spread to most of her trunk, face, and lower limbs. She was not systemically unwell. Her medical history included atrial fibrillation, cerebrovascular disease, hypertension, and an intertriginous reaction for which oral terbinafine 250 mg daily had been started three days before the rash began. Current long term drugs included aspirin, warfarin, alendronic acid, bisoprolol, calcium supplements, candesartan, furosemide, loperamide, and omeprazole. She had no known drug allergies. On examination, large confluent patches and plaques of oedematous erythema were present especially on the trunk, face, and lower limbs. The palms and soles were spared. Hundreds of small non-follicular based pustules were seen within these areas. No ulceration or blistering was seen. Blood tests showed normal renal and liver function, C reactive protein (31 mmol/L; normal 0-1.7), total white cell count (15.7 ×109/L; 4.0-11.0), neutrophil count (13.6×109/L; 2.5-7.5), lymphocyte count (1.36×109/L), eosinophil count (0.32×109/L; 0.04-0.44). Haemoglobin and platelet counts were within the normal range. A swab from a pustule showed no bacterial growth. Histological analysis showed subcorneal pustules. Terbinafine was stopped immediately and the patient was treated with topical steroids and emollients. The rash began to resolve within a week. ### 1 What is the diagnosis in this case of generalised pustulosis? #### Short answer On the basis of the history and clinical and histopathological findings the diagnosis is acute generalised exanthematous pustulosis. #### Long answer Acute generalised exanthematous pustulosis is an adverse cutaneous drug eruption in which many small sterile pustules develop within large areas of erythema (figure⇓), often within a few …