A perplexing rash.

To cite: Ranpara MP, Yesudian PD. BMJ Case Rep Published online: [please include Day Month Year] doi:10.1136/bcr-2015211792 DESCRIPTION A 69-year-old woman presented to the emergency department with a painful rash of 5 weeks duration. The rash started as two discrete erythematous plaques on the left medial malleolus and was treated as cellulitis by her general practitioner. Despite antibiotic treatment, the skin condition worsened and spread to her chest, abdomen, and upper and lower limbs. The patient had a history of Crohn’s disease for which she had started azathioprine 3 weeks prior to presentation, and poorly controlled type 2 diabetes that required insulin. On examination, she had erythematous plaques on the trunk and limbs, some of which had coalesced to form larger plaques in the lower limbs (figures 1 and 2). The rest of her systemic examination was unremarkable. The differential diagnosis considered in the Acute Medical Unit (AMU) included an adverse cutaneous drug reaction to azathioprine, erythema nodosum and insect bites. The patient’s azathioprine and clindamycin were stopped and a specialist review was requested. The dermatology team reviewed her and made a clinical diagnosis of Sweet’s syndrome secondary to inflammatory bowel disease. A punch biopsy from the rash on the left arm revealed papillary dermal oedema and an upper dermal infiltrate of neutrophils with leucocytoclasia, consistent with Sweet’s syndrome. First described by Robert Douglas Sweet in 1964, Sweet’s syndrome, or acute febrile neutrophilic dermatosis, is a constellation of neutrophilia, fever and erythematous plaques with a neutrophilic infiltrate on histology. It can be associated with malignancies, inflammatory bowel disease and drugs. The pathogenesis of this condition is unclear. Topical or systemic corticosteroids are the cornerstone of therapy, but potassium iodide and colchicines can also be considered. 2 Our patient made a full recovery within 5 days of applying topical clobetasol propionate (a potent topical steroid) on the lesions.