Tender skin plaques exuding yellow oil

A 47-year-old man was admitted to hospital with a six-week history of multiple tender plaques localised to his upper back, abdomen, buttocks and thighs. The plaques exuded a yellow, viscous, oily discharge (Figure 1). He had developed a fever and malaise. A deep skin biopsy revealed interstitial neutrophilia undergoing leucocytoclasis between the collagen bundles in the dermis. There was intense oedema with a mixed inflammatory infiltrate within the deeper dermis and an associated separation of the underlying fat outlined by a granulomatous reaction (Figure 2).