An 18 year-old-woman presented with a 1-week history of a psoriasiform eruption on her limbs and trunk that began 1 week after starting metformin hydrochloride. She had taken no other medications. She had no personal or family history of psoriasis. The lesions disappeared within 5 weeks after discontinuation of the drug. In the 4 months following the cessation of metformin hydrochloride, no relapse was observed, but rechallenge with oral metformin again produced the eruption. Metformin hydrochloride should be added to the list of drugs that can cause a psoriasiform eruption
