Multifocal fixed drug eruption mimicking erythema multiforme.

A 38-year-old woman presented with a widespread bullous eruption that recurred during menstruation. Skin biopsy suggested erythema multiforme. As she was receiving synthetic progesterones for dysmenorrhoea the diagnosis of an auto-immune progesterone dermatitis was considered. However, subsequent investigations confirmed the diagnosis to be a fixed drug eruption to mefenamic acid taken for dysmenorrhoea.